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Experiment 9 Implement Multistage Cascode and Cascade Amplifier Objective

This experiment aims to understand multistage amplifiers by implementing a cascade amplifier circuit using two BJTs. Key steps include: 1. Calculating the DC bias voltages and currents theoretically and measuring them experimentally. 2. Calculating the AC voltage gain of each transistor stage theoretically and measuring the overall gain experimentally. 3. Applying a 10mV input signal and using an oscilloscope to observe the input, output of the first stage, and overall output signals to ensure no distortion and compare measured and calculated gains.

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75 views4 pages

Experiment 9 Implement Multistage Cascode and Cascade Amplifier Objective

This experiment aims to understand multistage amplifiers by implementing a cascade amplifier circuit using two BJTs. Key steps include: 1. Calculating the DC bias voltages and currents theoretically and measuring them experimentally. 2. Calculating the AC voltage gain of each transistor stage theoretically and measuring the overall gain experimentally. 3. Applying a 10mV input signal and using an oscilloscope to observe the input, output of the first stage, and overall output signals to ensure no distortion and compare measured and calculated gains.

Uploaded by

ImMalik
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Experiment 9

Implement Multistage Cascode and Cascade Amplifier

Objective
● To understand multistage amplifier

Materials Needed
a. Breadboard
b. Connecting leads
c. Digital multimeter (DMM)
d. Resistor
● Rc2=1.8k
● Re=1k
● R1=6.8k
● R2=5.6k
● R3=4.7k,
e. Capacitor 10u F

Basic Information
A cascade circuit , as shown in fig.1 provides a common emmitter amplifier using Q1
directly connected to a common base amplifier using Q2. The voltage gain of stage Q1 is
approximately 1, with the voltage V 0 1 being opposite in polarity to that applied as

Av 1=-1

The voltage gain of stage Q2 is non inverted and of magnitude

Av 2 = Rc / re 2

Resulting in an overall gain

Av = Av 1 Av 2 = - Rc / re 2

Cascade Amplifier

a. Calculate DC bias voltage and currents in the cascade amplifier of fig.1(assuming


the base currents are much less than the voltage divider current).
Figure.1

Calculated V B1 =______________
Calculated V E1 =______________
Calculated V C1 =______________
Calculated V B2 =______________
Calculated V E2 =______________
Calculated V C2 =______________

Calculate the DC bias emitter current


Calculated I E1 =______________
Calculated I E2 =______________

Calculate the transistor dynamic resistances

Calculated re1 =______________


Calculated re2 =______________

b. Connect the cascade circuit of fig.1. measure and record DC bias voltages.

Measured V B1 =______________
Measured V E1 =______________
Measured V C1 =______________
Measured V B2 =______________
Measured V E2 =______________
Measured V C2 =______________

Measure the values of emmitter current

I E1 =______________
I E2 =______________

And the values of dynamic resistance

re1 =______________
re2 =______________

c. Using Equations calculate the AC voltage gain of each transistor stage.

Calculated Av 1=______________
Calculated Av 2=______________

d. Apply input signal, V sig =10mV , peak at f=10k Hz. Using the oscilloscope
observe the output waveform V 0 to make sure that no signal distortion occurs. If
the output is clipped or distorted reduce the input signal until the clipping or
distortion disappears. Using the DMM measure , record the AC signals.

Measured V i =_______________

Measured V 01 =______________

Measured V 02 =______________

Calculate the measured voltage gain

Av = V 0 2 / V i =_______________

Av 1 = V 0 1 / V i = _______________
Av 2 = V 0 2 / V 0 1 =_______________

Compare the measured voltages gains with those calculated in steps c and d.

e. Using the oscilloscope, observe and record waveforms for the input signal, V i ,
output of stage 1, V 0 1, and output of stage 2, V 0 2. Show amplitude and phase
relations clearly.

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