What is ”Signal Conditioning”?

Types of Signal Conditioning

Current Amplification

Electronics
Signal Conditioning

Terry Sturtevant

Wilfrid Laurier University

October 9, 2012

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

What is “Signal Conditioning”?

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

What is “Signal Conditioning”?

There are many factors which may prevent a signal produced

by one device or circuit from being usable by another device or
circuit, requiring some intermediate circuitry to bridge the gap.

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

What is “Signal Conditioning”?

There are many factors which may prevent a signal produced

by one device or circuit from being usable by another device or
circuit, requiring some intermediate circuitry to bridge the gap.
This kind of “bridging” function is doing what I call “signal
conditioning”.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Types of Signal Conditioning

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Types of Signal Conditioning

Signal conditioning may be divided into 4 types:

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Types of Signal Conditioning

Signal conditioning may be divided into 4 types:

1 analog; analog signal in, analog signal out

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Types of Signal Conditioning

Signal conditioning may be divided into 4 types:

1 analog; analog signal in, analog signal out
2 digital; digital signal in, digital signal out

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Types of Signal Conditioning

Signal conditioning may be divided into 4 types:

1 analog; analog signal in, analog signal out
2 digital; digital signal in, digital signal out
3 either; either kind of signal in; same type out

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Types of Signal Conditioning

Signal conditioning may be divided into 4 types:

1 analog; analog signal in, analog signal out
2 digital; digital signal in, digital signal out
3 either; either kind of signal in; same type out
4 interface; involves both analog and digital signals in some way

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting
filtering

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting
filtering
impedance changing

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting
filtering
impedance changing
All of the above functions can be performed by operational
amplifier circuits.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting
filtering
impedance changing
All of the above functions can be performed by operational
amplifier circuits. A couple of additional functions are

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting
filtering
impedance changing
All of the above functions can be performed by operational
amplifier circuits. A couple of additional functions are
clipping

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Signal Conditioning

amplification or attenuation
level shifting
filtering
impedance changing
All of the above functions can be performed by operational
amplifier circuits. A couple of additional functions are
clipping
clamping

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Amplification

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Attenuation

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Inversion

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Level shifting

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clamping

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Often it’s necessary to ensure that a signal does not exceed a

certain voltage in order to avoid harming circuitry which
follows.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Often it’s necessary to ensure that a signal does not exceed a

certain voltage in order to avoid harming circuitry which
follows.
For instance, a sensor inside the engine of a car may pick up
electrical noise of hundreds of volts occasionally which could
destroy a microprocessor.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Often it’s necessary to ensure that a signal does not exceed a

certain voltage in order to avoid harming circuitry which
follows.
For instance, a sensor inside the engine of a car may pick up
electrical noise of hundreds of volts occasionally which could
destroy a microprocessor.
To avoid this, the signal may be clipped so that it never goes
above a fixed voltage.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Often it’s necessary to ensure that a signal does not exceed a

certain voltage in order to avoid harming circuitry which
follows.
For instance, a sensor inside the engine of a car may pick up
electrical noise of hundreds of volts occasionally which could
destroy a microprocessor.
To avoid this, the signal may be clipped so that it never goes
above a fixed voltage.
This can be done using a Zener diode.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clipping

Often it’s necessary to ensure that a signal does not exceed a

certain voltage in order to avoid harming circuitry which
follows.
For instance, a sensor inside the engine of a car may pick up
electrical noise of hundreds of volts occasionally which could
destroy a microprocessor.
To avoid this, the signal may be clipped so that it never goes
above a fixed voltage.
This can be done using a Zener diode.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi

Rz
Vo

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The Zener diode will conduct once the voltage exceeds the
Zener voltage, VZ ,.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The Zener diode will conduct once the voltage exceeds the
Zener voltage, VZ ,.
The output voltage will follow the input until the input
exceeds VZ .

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The Zener diode will conduct once the voltage exceeds the
Zener voltage, VZ ,.
The output voltage will follow the input until the input
exceeds VZ .
From then on the output will not increase.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The Zener diode will conduct once the voltage exceeds the
Zener voltage, VZ ,.
The output voltage will follow the input until the input
exceeds VZ .
From then on the output will not increase.
The resistor should be chosen so that the maximum current
through the diode is within the specified limits.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clamping

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clamping

It may sometimes be necessary to ensure that a signal does

not become negative.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clamping

It may sometimes be necessary to ensure that a signal does

not become negative.
Again, using the car sensor example, a negative voltage due to
noise could destroy a microprocessor.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clamping

It may sometimes be necessary to ensure that a signal does

not become negative.
Again, using the car sensor example, a negative voltage due to
noise could destroy a microprocessor.
To avoid this, the signal may be clamped so that it never
goes below zero.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Clamping

It may sometimes be necessary to ensure that a signal does

not become negative.
Again, using the car sensor example, a negative voltage due to
noise could destroy a microprocessor.
To avoid this, the signal may be clamped so that it never
goes below zero.
This can be done using a diode.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi

Rd
Vo

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The diode will conduct once it is forward biased.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The diode will conduct once it is forward biased.

The output voltage will follow the input until the input goes
below about −0.7V .

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The diode will conduct once it is forward biased.

The output voltage will follow the input until the input goes
below about −0.7V .
From then on the output will not decrease.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The diode will conduct once it is forward biased.

The output voltage will follow the input until the input goes
below about −0.7V .
From then on the output will not decrease.
(This slight negative voltage will not be a problem for most
electronics.)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The diode will conduct once it is forward biased.

The output voltage will follow the input until the input goes
below about −0.7V .
From then on the output will not decrease.
(This slight negative voltage will not be a problem for most
electronics.)
The resistor should be chosen so that the maximum current
through the diode is within the specified limits.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Digital

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Digital

Sometimes digital signals in a system need to be cleaned up.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Digital

Sometimes digital signals in a system need to be cleaned up.

This can be in order to do one or both of:

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Digital

Sometimes digital signals in a system need to be cleaned up.

This can be in order to do one or both of:
remove noise from the signal

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Digital

Sometimes digital signals in a system need to be cleaned up.

This can be in order to do one or both of:
remove noise from the signal
change the duration of the signal

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Digital

Sometimes digital signals in a system need to be cleaned up.

This can be in order to do one or both of:
remove noise from the signal
change the duration of the signal
These two cases will now be discussed.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Removing Noise

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Removing Noise

Detecting the state of a digital signal can be difficult if the

signal contains noise.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Removing Noise

Detecting the state of a digital signal can be difficult if the

signal contains noise.
A Schmitt trigger is a gate which uses hysteresis to remove
noise from a signal.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Removing Noise

Detecting the state of a digital signal can be difficult if the

signal contains noise.
A Schmitt trigger is a gate which uses hysteresis to remove
noise from a signal.
This is in contrast to an ordinary gate, where the output
changes state as the input passes some unknown voltage
between the manufacturer’s specified Vilmax and Vihmin .

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

For a Schmitt trigger, there are two separate voltages.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

For a Schmitt trigger, there are two separate voltages.

When the output is low, the input has to go above Von before
the output will go high,

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

For a Schmitt trigger, there are two separate voltages.

When the output is low, the input has to go above Von before
the output will go high,
and when the output is high, the input has to go below Voff
before the output will go low.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

For a Schmitt trigger, there are two separate voltages.

When the output is low, the input has to go above Von before
the output will go high,
and when the output is high, the input has to go below Voff
before the output will go low.
The farther apart Von and Voff are, the more noise immunity
is provided.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

For a Schmitt trigger, there are two separate voltages.

When the output is low, the input has to go above Von before
the output will go high,
and when the output is high, the input has to go below Voff
before the output will go low.
The farther apart Von and Voff are, the more noise immunity
is provided.
(For a normal gate, is it as though Von and Voff are the same.)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Normal TTL transfer characteristic

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Von = Voff

Normal TTL transfer characteristic

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Schmitt trigger transfer characteristic; (i.e. with hysteresis)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Von

Schmitt trigger transfer characteristic; (i.e. with hysteresis)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Voff

Schmitt trigger transfer characteristic; (i.e. with hysteresis)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Von

Voff

Schmitt trigger transfer characteristic; (i.e. with hysteresis)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi
Von
Voff

Vo

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

A common situation occurs when a signal needs to be

extended in time so that it will be detected by a
microprocessor.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

A common situation occurs when a signal needs to be

extended in time so that it will be detected by a
microprocessor.
This can be accomplished by the use of a one shot.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

A common situation occurs when a signal needs to be

extended in time so that it will be detected by a
microprocessor.
This can be accomplished by the use of a one shot.
When a trigger pulse (ie. the signal) is received by a one
shot, its output will produce a pulse of a fixed length.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

A common situation occurs when a signal needs to be

extended in time so that it will be detected by a
microprocessor.
This can be accomplished by the use of a one shot.
When a trigger pulse (ie. the signal) is received by a one
shot, its output will produce a pulse of a fixed length.
There are two types of one shots:

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

A common situation occurs when a signal needs to be

extended in time so that it will be detected by a
microprocessor.
This can be accomplished by the use of a one shot.
When a trigger pulse (ie. the signal) is received by a one
shot, its output will produce a pulse of a fixed length.
There are two types of one shots:
retriggerable

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Changing Pulse Width

A common situation occurs when a signal needs to be

extended in time so that it will be detected by a
microprocessor.
This can be accomplished by the use of a one shot.
When a trigger pulse (ie. the signal) is received by a one
shot, its output will produce a pulse of a fixed length.
There are two types of one shots:
retriggerable
non-retriggerable

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

non-retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

non-retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

non-retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

trigger

non-retriggerable output

retriggerable output

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

With a retriggerable one shot, if a second trigger pulse occurs

while the output is active (ie. during a pulse created by a
previous trigger pulse), the output will be extended for a
further period.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

With a retriggerable one shot, if a second trigger pulse occurs

while the output is active (ie. during a pulse created by a
previous trigger pulse), the output will be extended for a
further period.
In this way a pulse can be extended indefinitely.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

With a retriggerable one shot, if a second trigger pulse occurs

while the output is active (ie. during a pulse created by a
previous trigger pulse), the output will be extended for a
further period.
In this way a pulse can be extended indefinitely.
With a non-retriggerable one shot, any trigger pulses
occurring while the output is active, (ie. during a pulse
created by a previous trigger pulse), will be ignored.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

With a retriggerable one shot, if a second trigger pulse occurs

while the output is active (ie. during a pulse created by a
previous trigger pulse), the output will be extended for a
further period.
In this way a pulse can be extended indefinitely.
With a non-retriggerable one shot, any trigger pulses
occurring while the output is active, (ie. during a pulse
created by a previous trigger pulse), will be ignored.
In other words, the output pulse is always the same length.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Either

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Either

The purpose of isolation is to remove large DC offsets from a

signal.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Either

The purpose of isolation is to remove large DC offsets from a

signal.
(Of course it could be to add a DC offset instead.)
An op-amp can be used to remove small DC offsets, of the
same order of voltage as the supply voltage.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Either

The purpose of isolation is to remove large DC offsets from a

signal.
(Of course it could be to add a DC offset instead.)
An op-amp can be used to remove small DC offsets, of the
same order of voltage as the supply voltage.
Sometimes hundreds or thousands of volts must be removed.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Either

The purpose of isolation is to remove large DC offsets from a

signal.
(Of course it could be to add a DC offset instead.)
An op-amp can be used to remove small DC offsets, of the
same order of voltage as the supply voltage.
Sometimes hundreds or thousands of volts must be removed.
(For instance, inside a car engine, the ignition system
produces sparks of thousands of volts, while the electronics
runs on normal logic levels.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Either

The purpose of isolation is to remove large DC offsets from a

signal.
(Of course it could be to add a DC offset instead.)
An op-amp can be used to remove small DC offsets, of the
same order of voltage as the supply voltage.
Sometimes hundreds or thousands of volts must be removed.
(For instance, inside a car engine, the ignition system
produces sparks of thousands of volts, while the electronics
runs on normal logic levels.
The spark plug voltages could not be directly sensed by the
microprocessor. At least more than once.....)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Inductive isolation using a transformer

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Inductive isolation using a transformer

cannot transmit DC (ie. steady-state) values

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Inductive isolation using a transformer

cannot transmit DC (ie. steady-state) values
2 way

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Inductive isolation using a transformer

cannot transmit DC (ie. steady-state) values
2 way
can transmit power

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Inductive isolation using a transformer

cannot transmit DC (ie. steady-state) values
2 way
can transmit power
the above two conditions mean that care must be taken as
voltage spikes at the input end can be transmitted to the
input end and vice versa

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Keep in mind that different numbers of windings in the two coils

allow the input signal to be increased or decreased while any DC
offset is removed.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi Vo

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Optical isolation using an LED and a phototransistor or

photodiode

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Optical isolation using an LED and a phototransistor or

photodiode
can transmit DC (ie. steady-state values)

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Optical isolation using an LED and a phototransistor or

photodiode
can transmit DC (ie. steady-state values)
only one way

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Optical isolation using an LED and a phototransistor or

photodiode
can transmit DC (ie. steady-state values)
only one way
cannot transmit power

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Optical isolation using an LED and a phototransistor or

photodiode
can transmit DC (ie. steady-state values)
only one way
cannot transmit power
the above two conditions mean that there is no danger of
voltage spikes as there is with inductive isolation

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The resistors are used because effectively the LED and the
phototransistor are current devices, and usually signals are
processed as voltages.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The resistors are used because effectively the LED and the
phototransistor are current devices, and usually signals are
processed as voltages.
The values chosen for the resistors should be consistent with
the current specifications for the device.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The resistors are used because effectively the LED and the
phototransistor are current devices, and usually signals are
processed as voltages.
The values chosen for the resistors should be consistent with
the current specifications for the device.
The amount of DC isolation provided by an optoisolator is
usually in the range of kV.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

The resistors are used because effectively the LED and the
phototransistor are current devices, and usually signals are
processed as voltages.
The values chosen for the resistors should be consistent with
the current specifications for the device.
The amount of DC isolation provided by an optoisolator is
usually in the range of kV.
At some point the insulation will break down and arcs can
occur.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi Vs

Ri

Vo
Ro

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Whenever sensors are in a place where it is possible for high

voltages to be induced, optical isolation should be used to protect
electronic devices which follow.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Comparators

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Comparators

Two analog voltages can be compared with an analog

comparator.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Comparators

Two analog voltages can be compared with an analog

comparator.
This device is basically an operational amplifier with a digital
output, so that the output indicates which of the inputs is
higher.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Switches and Multiplexers

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Analog Switches and Multiplexers

An analog switch works just like a mechanical switch in allowing

an analog signal to flow between two points in a circuit when it is
closed, and preventing the flow when it is open. The difference
with an analog switch is that the control of the opening and
closing of the switch is provided by a digital signal. Like
mechanical switches, there are a variety of switch types, such as
SPST, SPDT, DPDT, and so on. The resistor Ron is to indicate a
finite resistance between the input and output when the switch is
closed. The value of Ron should be in the device specifications.

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi Ron Vo

Vc

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi Ron Vo

Vc

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

Vi Ron Vo

Vc

Terry Sturtevant Electronics Signal Conditioning

 Analog Signal Conditioning
What is ”Signal Conditioning”?
Digital
Types of Signal Conditioning
Either
Current Amplification
Interface

An analog multiplexer is similar to a digital multiplexer in that a

set of digital signals controls which analog signal is passed through
to the output. Since the internal construction is similar to that of
an analog switch, there is an on resistance as before.

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Current Amplification

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Current Amplification

Operational amplifiers make good voltage amplifiers, but usually

their current output is very limited. Current amplification is a job
more suited to transistors.

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Basic BJT Operation

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Basic BJT Operation

The BJT operates as a current amplifier. In the common emitter

configuration, controlling the current to the base results in change
to the collector current. Since
Ic
β= ≈ 100 → 500
Ib
then a substantial increase in current is possible. A few choices of
how to do this in a circuit follow. (NPN transistors will be
assumed. It’s easy to change to PNP after you understand the
principles.)

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Darlington Transistors

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Darlington Transistors

If a very great current gain is desired, ie. up to ≈ 1000×, a

Darlington configuration may be used. This has the emitter of
one transistor fed directly into the base of another, with the
collectors in common. In this way the two β values get multiplied,
so a much greater gain is possible. Darlington transistors are
devices which are connected this way internally, so they look like
an ordinary transistor from the outside.

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Grounded Load

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Grounded Load

In this configuration, the load , shown as a resistance Rl , is placed

between the emitter of the transistor and ground. It is often useful
to have one end of the load grounded. For a transistor to be “on”,
the base–emitter junction must be forward biased so

Vbe ≥ 0.7V

This means that the base of the transistor must be able to go

above the highest load voltage desired.

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Floating Load

Terry Sturtevant Electronics Signal Conditioning

 What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Floating Load

If the base voltage cannot easily be raised above the desired load
voltage, it is possible to place the load between the collector of the
transistor and the supply voltage, and then ground the emitter of
the transistor.

Terry Sturtevant Electronics Signal Conditioning

What is ”Signal Conditioning”?
Types of Signal Conditioning
Current Amplification

Vsupply

Rc1

Rb1 β2
Vin Vo
β1 Rb2

RL

Terry Sturtevant Electronics Signal Conditioning