47.3.5. Input Impedance

Try these first

1. 1.

   Define input impedance.

   Hint

   Think about what the amplifier accepts.

2. 2.

   What is voltage gain?

   Hint

   Consider how much the signal is amplified.

3. 3.

   What does high input impedance help prevent?

   • Signal attenuation
   • Signal integrity loss
   • Increased noise

   Hint

   Think about how the circuit interacts with the previous one.

4. 4.

   True or False: The ideal voltage gain for a buffer amplifier is less than 1.

   • True
   • False

   Hint

   Remember what a buffer does in an amplifier configuration.

5. 5.

   Determine the input impedance of a common collector amplifier with configurations leading to a base current of 10 µA, load current of 0.5 mA, β of 120, and resistance of 4.7kΩ.

   Hint

   Start by calculating each term separately.

6. 6.

   Analyze how changes in load capacitance to 10 pF from 100 pF alters the performance characteristics of a common drain amplifier with respect to its upper cutoff frequency.

   Hint

   Plug into the upper cutoff formula and see the difference.