# 6.8 Exercises

Unless otherwise specified, use ß=100.

## Analysis Problems

1. Determine the input and output impedances of the circuit of Figure 6.8.1.
2. Determine the load voltage for the circuit of Figure 6.8.1 if Vin is 10 mV.
3. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.2 if Vin is 70 mV.
4. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.3 if Vin is 50 mV.
5. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.4 if Vin is 25 mV.
6. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.5 if Vin is 30 mV.
7. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.6 if Vin is 60 mV.
8. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.7 if Vin is 150 mV.
9. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.8 if Vin is 200 mV.
10. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.9 if Vin is 250 mV.
11. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.10 if Vin is 300 mV.
12. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.11 if Vin is 50 mV.
13. Determine Zin, Zout, and the load voltage for the circuit of Figure 6.8.12 if Vin is 2 mV.

## Design Problems

1. Redesign the circuit of Figure 6.8.2 to halve the existing gain while keeping the Q point where it is currently.
2. By using a Darlington pair, redesign the circuit of Figure 6.8.3 to double Zin.
3. Redesign the circuit of Figure 6.8.3 so that it exhibits the same performance parameters but uses a PNP device.
4. Redesign the circuit of Figure 6.8.5 to double the existing gain while keeping the Q point where it is currently.
5. Redesign the circuit of Figure 6.8.7 so that it exhibits the same performance parameters but uses an NPN device.

## Challenge Problems

1. Determine the gain and input impedance for the circuit of Figure 6.8.13.
VCC = 20 V, VEE = −10 V, RB = 18 kΩ, RE1= 10 kΩ, RC1 = 12 kΩ, R1 = 33 kΩ,
R2 = 15 kΩ, RE2 = 5.6 kΩ, RSW = 400 kΩ, RC2 = 6.8 kΩ, RL = 24 kΩ.

2. For the circuit of Figure 6.8.10, replace its load resistor with the circuit of Figure 6.8.6 and determine the combined gain and input impedance of the system.

## Computer Simulation Problems

1. Use a transient analysis to verify the load voltage of problem 3.
2. Use a transient analysis to verify the load voltage of problem 4.
3. Use a transient analysis to verify the load voltage of problem 8.
4. Consider the amplifier of Figure 6.8.1. Replace the 4.3 kΩ emitter resistor with a potentiometer of the same value. Connect the wiper arm to the emitter bypass capacitor. Run several transient analyses at different pot settings (0%, 25%, 50%, etc.). What can you conclude from the results?