27.6. Output Resistance Analysis

Try these first

1. 1.

   Define voltage gain in a common emitter amplifier.

   Hint

   Think about what it represents regarding the input and output levels.

2. 2.

   What does the emitter resistor (RE) do?

   Hint

   Consider how changing components affect the voltage levels.

3. 3.

   What is the formula for voltage gain in a common emitter amplifier?

   • A = - gm * RE / RC
   • A = - gm * RC / (1 + gm * RE)
   • A = gm * RE / RC

   Hint

   Remember the roles of gm and resistors in the gain calculation.

4. 4.

   True or False: The presence of an emitter resistor (RE) always increases voltage gain.

   • True
   • False

   Hint

   Think about the dual role of RE in the circuit.

5. 5.

   Design a common emitter amplifier that achieves a voltage gain of -15 with noted constraints of sigma voltage sources. Discuss how to maintain an operating point.

   Hint

   Focus on practical resistor designs related to gain expressions.

6. 6.

   Analyze the scenario where you replace RE with a capacitor. What changes occur in gain and stability? Provide calculations.

   Hint

   Think of AC analysis differentiating impacts on both frequency responses.