47.3.6. Output Impedance Calculation

Try these first

1. 1.

   What is output impedance?

   Hint

   Think about what 'impedance' means in a circuit context.

2. 2.

   Name one small signal parameter.

   Hint

   It’s related to the current flowing in the transistor.

3. 3.

   What is the formula for calculating output impedance?

   • R_out = R_load + small signal parameters
   • Z_out = 1 / (g_m + g_o)
   • Z_out = R_load + R_bias

   Hint

   Think about how output and small signal parameters relate.

4. 4.

   True or False: Lower output impedance is always better for amplifier performance.

   • True
   • False

   Hint

   Consider what happens when the impedance is high.

5. 5.

   Given a common collector amplifier with a collector current of 0.75 mA, calculate the output impedance if the small signal parameters g_m = 40 mS and r_o = 200 kΩ.

   Hint

   Substitute the values carefully into the formula.

6. 6.

   Consider a scenario where a load resistance of 1kΩ is connected. If the output impedance calculated is 52Ω, what is the effect of this load on the output voltage?

   Hint

   Think about voltage division principles and how impedance interacts.