19.1.7. Small Signal Parameters

Try these first

1. 1.

   Define transconductance.

   Hint

   Think about the relationship between current and voltage in a transistor.

2. 2.

   What does the symbol r_π represent?

   Hint

   Consider what resistance looks into the base-emitter junction.

3. 3.

   What does transconductance refer to?

   • Change in collector current per change in base current
   • Change in collector current per change in base-emitter voltage
   • Input resistance of the transistor

   Hint

   Think about how transistors amplify voltage changes.

4. 4.

   True or False: The output conductance is inversely related to output resistance.

   • True
   • False

   Hint

   Consider their definitions.

5. 5.

   Given a BJT with a collector current of 4 mA and a transconductance of 1.5 mS, calculate the change in collector current for a change of 0.1 V in V_BE.

   Hint

   Use the transconductance formula to find the change.

6. 6.

   Analyze how varying the base-emitter voltage affects the current gain of a BJT amplifier. Explain how the operating point affects your analysis.

   Hint

   Consider how the gain relates to voltage changes.