Consider the series-shunt feedback circuit in Figure
Figure P12.37
(a)
The small signal parameter for
Answer to Problem 12.37P
The trans-conductance of the first transistor
Explanation of Solution
Given:
The given circuit is shown in Figure 1
Calculation:
The value of the Thevenin voltage is given by,
The expression for the equivalent resistance is given by,
The expression for the current
Substitute
The expression to determine the value of the collector current
Substitute
The expression for the collector voltage
Substitute
The expression for the value of the current
Substitute
The expression for the collector voltage
Substitute
The expression for the value of the current
Substitute
The expression for the small signal input resistance is given by,
Substitute
The expression for the trans-conductance of the first transistor is given by,
Substitute
The expression for the small signal input resistance is given by,
Substitute
The expression for the trans-conductance of the first transistor is given by,
Substitute
The expression for the small signal input resistance is given by,
Substitute
The expression for the trans-conductance of the first transistor is given by,
Substitute
Conclusion:
Therefore, the trans-conductance of the first transistor
(b)
The value of the small signal voltage gain
Answer to Problem 12.37P
The value of small signal voltage gain is 20.7.
Explanation of Solution
Given:
The given circuit is shown in Figure 1
Calculation:
Mark the values and draw the small signal equivalent circuit.
The required diagram is shown in Figure 2
The expression for the input voltage
Apply KCL at the node 1
Substitute
Substitute
Apply KCL at node 2.
Substitute
Apply KCL at the node 3
Substitute
Substitute
Apply KCL at the node 4
Substitute
Substitute
Substitute
Substitute
Conclusion:
Therefore, the value of small signal voltage gain is 20.7.
(c)
The value of the resistance
Answer to Problem 12.37P
The value of the input resistance is
Explanation of Solution
Given:
The given circuit is shown in Figure 1
Calculation:
The expression to determine the value of the current
Substitute
The value of
Substitute
The expression for the current
Substitute
The expression for the input current
Substitute
Conclusion:
Therefore, the value of the input resistance is
(d)
The value of the resistance
Answer to Problem 12.37P
The value of the output resistance is
Explanation of Solution
Given:
The given circuit is shown in Figure 1
Calculation:
Consider the equation (1).
Substitute
The equation for
Substitute
Consider the equation given,
Substitute
Substitute
Conclusion:
Therefore, the value of the output resistance is
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Chapter 12 Solutions
Microelectronics: Circuit Analysis and Design
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