IC 741
The most commonly used op-amp is IC741.
The 741 op-amp is a voltage amplifier.
Pin Configuration:
Let’s see the pin configuration and testing of 741 op-amps.
Usually, this is a numbered counter clockwise around the chip.
It is an 8 pin IC. They provide superior performance in
integrator, summing amplifier and general feedback
applications. These are high gain op-amp; the voltage on the
inverting input can be maintained almost equal to Vin.
It is a 8-pin dual-in-line package with a pin out shown above.
Pin 1: Offset null.
Pin 2: Inverting input terminal.
Pin 3: Non-inverting input terminal.
Pin 4: –VCC (negative voltage supply).
Pin 5: Offset null.
Pin 6: Output voltage.
Pin 7: +VCC (positive voltage supply).
Pin 8: No Connection.
The main pins in the 741 op-amp are pin2, pin3 and pin6. In
inverting amplifier, a positive voltage is applied to pin2 of the
op-amp; we get output as negative voltage through pin 6. The
polarity has been inverted. In a non-inverting amplifier, a
positive voltage is applied to pin3 of the op-amp; we get output
as positive voltage through pin 6. Polarity remains the same in
non-inverting amplifier. Vcc is usually in the range from 12 to
15 volts. When two supplies (+Vcc/-Vcc) are used, they are the
same voltage and of opposite sign in almost all cases.
Remember that the operational amplifier is a high gain,
differential voltage amplifier. For a 741 operational amplifier,
the gain is at least 100,000 and can be more than a million
(1,000,000). That’s an important fact you’ll need to remember
as you put the 741 into a circuit.
IC 741 Op Amp (Operational Amplifier)
The 741 Op Amp IC is a monolithic integrated circuit,
comprising of a general purpose Operational Amplifier. It was
first manufactured by Fairchild semiconductors in the year
1963. The number 741 indicates that this operational amplifier
IC has 7 functional pins, 4 pins capable of taking input and 1
output pin.
IC 741 Op Amp can provide high voltage gain and can be
operated over a wide range of voltages, which makes it the
best choice for use in integrators, summing amplifiers and
general feedback applications. It also features short circuit
protection and internal frequency compensation circuits built in
it. This Op-amp IC comes in the following form factors:
8 Pin DIP Package
TO5-8 Metal can package
8 Pin SOIC
NOTE: The manufacturer of the first IC in the above picture in
8-pin DIP Package is ST Microelectronics and that of the third IC
in 8-pin SOIC format is Texas Instruments. We couldn’t find the
information on the manufacturer of the second TO5-8 Metal
can package IC.
Pin out of IC 741 Op Amp and their Functions
The below figure illustrates the pin configurations and internal
block diagram of IC 741 in 8 pin DIP and TO5-8 metal can
package.
Now let’s take a look at the functions of different pins of 741 IC:
Pin4 & Pin7 (Power Supply): Pin7 is the positive voltage
supply terminal and Pin4 is the negative voltage supply
terminal. The 741 IC draws in power for its operation
from these pins. The voltage between these two pins can
be anywhere between 5V and 18V.
Pin6 (Output): This is the output pin of IC 741. The
voltage at this pin depends on the signals at the input pins
and the feedback mechanism used. If the output is said to
be high, it means that voltage at the output is equal to
positive supply voltage. Similarly, if the output is said to
be low, it means that voltage at the output is equal to
negative supply voltage.
Pin2 & Pin3 (Input): These are input pins for the IC. Pin2 is
the inverting input and Pin3 is the non-inverting input. If
the voltage at Pin2 is greater than the voltage at Pin3, i.e.,
the voltage at inverting input is higher, the output signal
stays low. Similarly, if the voltage at Pin3 is greater than
the voltage at Pin2, i.e., the voltage at non-inverting input
is high, the output goes high.
Pin1 & Pin5 (Offset Null): Because of high gain provided
by 741 Op-Amp, even slight differences in voltages at the
inverting and non-inverting inputs, caused due to
irregularities in manufacturing process or external
disturbances, can influence the output. To nullify this
effect, an offset voltage can be applied at pin1 and pin5,
and is usually done using a potentiometer.
Pin8 (N/C): This pin is not connected to any circuit inside
741 IC. It’s just a dummy lead used to fill the void space in
standard 8 pin packages.
Specifications
The following are the basic specifications of IC 741:
Power Supply: Requires a Minimum voltage of 5V and can
withstand up to 18V
Input Impedance: About 2 M Ω
Output impedance: About 75 Ω
Voltage Gain: 200,000 for low frequencies (200 V / m V)
Maximum Output Current: 20 m A
Recommended Output Load: Greater than 2 K Ω
Input Offset: Ranges between 2 m V and 6 m V
Slew Rate: 0.5V/µS (It is the rate at which an Op-Amp can
detect voltage changes)
The high input impedance and very small output impedance
makes IC 741 a near ideal voltage amplifier.
NOTE: The above mentioned specifications are generic and may
vary from manufacturer to manufacturer. To get accurate
information, please refer to the data sheet.
