Concept explainers
Consider the diff-amp shown in Figure P 11.62 . The circuit parameters are
(a)
To sketch: The small signal equivalent circuit for the differential amplifier.
Answer to Problem 11.62P
The small signal circuit is shown in Figure 2.
Explanation of Solution
Given:
The given circuit is shown below.
Calculation:
The small signal equivalent circuit for the above circuit is shown in Figure 1.
Figure 1
Because of symmetry the value of the currents
The value of the currents
The value of the currents
The value of the currents
For differential up circuit emitter current
Modify the circuit, the required diagram is shown in Figure 2
Figure 2
Conclusion:
Therefore, the small signal circuit is shown in Figure 3
(b)
The value of one sided differential voltage gain.
Answer to Problem 11.62P
The value of the differential mode voltage gain is
Explanation of Solution
Given:
The given circuit is shown below.
Calculation:
Consider the left portion of the circuit as,
Figure 3
Modify the circuit as shown in Figure 4
Figure 4
The expression for the output voltage of the above circuit is given by,
The emitter current of the transistor is calculated as,
The expression for the collector current of the transistor
Substitute
Apply KCL at the output node
Substitute
The transconductance of transistor
The transconductance of transistor
The small signal output resistance of
The small signal output resistance of
The small signal resistance
The value of the voltage
Conclusion:
Therefore, the value of the differential mode voltage gain is
(c)
The differential voltage gain of both the sides.
Answer to Problem 11.62P
The value of differential voltage gain is
Explanation of Solution
Given:
The given circuit is shown below.
Calculation:
The expression for the output voltage of the above circuit is given by,
The value of the voltage
Conclusion:
Therefore, the value of differential voltage gain is
(d)
The value of the differential voltage gain of both the sides.
Answer to Problem 11.62P
The value of differential voltage gain is
Explanation of Solution
Given:
The given circuit is shown below.
Calculation:
The expression to determine the value of the two sided differential voltage gain is given by,
Conclusion:
Therefore, the value of differential voltage gain is
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Chapter 11 Solutions
MICROELECT. CIRCUIT ANALYSIS&DESIGN (LL)
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