68.1.9. Small Signal Gain and Resistance

Try these first

1. 1.

   Define transconductance and provide its formula.

   Hint

   Think about how output current responds to variations in input voltage.

2. 2.

   What is the role of early voltage in a transistor?

   Hint

   Consider how transistors behave at different collector voltages.

3. 3.

   What is the formula for transconductance?

   • I_D/V_{GS}
   • V_{GS}/I_D
   • I_C/R

   Hint

   Refer to how input voltage influences output current.

4. 4.

   True or False: A higher output resistance in an amplifier typically increases the gain.

   • True
   • False

   Hint

   Think about the formula where gain is the product of transconductance and output resistance.

5. 5.

   Given a circuit with transistor Q1 having a transconductance of 15 mS and an output resistance of 20 kΩ, calculate the voltage gain. Then analyze how this would change if the load capacitance increased.

   Hint

   Draw the small-signal model to visualize changes in the circuit.

6. 6.

   Consider an amplifier where the early voltage is given as 100V, and the collector current is set to 2 mA. Calculate the increased output resistance and its effects on amplification when adjusting the collector-emitter voltage.

   Hint

   Relate increased resistance to the operational limits of gain.