Output impedance with a resistor r across the constant

Question

Use the two diode model linearized as below

Where β = IC/IB is the current gain, and r_e is given by the diode equation (m = 1) as 25 mV/i_e at room temperature.

Note: This is a linear model of the transistor. So we are assuming we have biased it at a suitable DC operating point which provides r_c, as a known given value. When using a linearized model we are looking for an AC/small signal analysis.

With emitter grounded calculate

a) Input impedance at the base.

b) Output impedance at the collector

c) Output impedance with a resistor R across the constant current source (from the collector terminal to the base terminal)

With base grounded calculate

d) Impedance at the emitter

e) Output impedance at the collector

f) Output impedance at the collector with a resistor R across the constant current source.

With an impedance W to ground at the base

g) Impedance at the emitter