25.2.3. Higher Frequency Effects on BJT

Try these first

1. 1.

   What is the small signal model used for?

   Hint

   Think about AC signals and their effects on DC circuits.

2. 2.

   Name the two parasitic capacitances in BJTs.

   Hint

   Consider the connections of the transistor terminals.

3. 3.

   What does the small signal model assume about DC signals?

   • They are zero
   • They are large
   • They are fixed

   Hint

   Consider the implications of 'small signal' analysis.

4. 4.

   True or False: Parasitic capacitances have no effect at low frequencies.

   • True
   • False

   Hint

   How do capacitances influence frequencies?

5. 5.

   Design a Common Emitter amplifier circuit that includes measures to handle potential thermal runaway issues. Discuss what elements will enhance stability.

   Hint

   Think about how feedback works in stabilizing circuits.

6. 6.

   If a BJT has an Early voltage of 100V and a collector-emitter voltage of 10V, calculate how the output current might change when the voltage increases to 20V.

   Hint

   Refer to the changes in collector current with respect to V_ce variations.