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ECSE-2210 Microelectronics Technology
Fall 2005
Class Activity 22
The material for this class activity can be found in Chapter 12, pp 449-458.
The npn switching transistor used in the circuit below has the following parameters:
Minority carrier lifetime in base,
τ
B = 100 ns;
β
dc = 50. Assume
γ
= 1. Answer the following
questions.
Assume RB is 100 kΩ. At t = 0, the switch is turned on. (i.e., the base current increases from
0 to approximately to 0.1 mA at t = 0).
a. Will the transistor be in saturation or forward active mode for t >> 0, i.e. t = ∞? What
will be the final value of the collector current?
b. Calculate and plot the charge stored in the base, QB as a function of time,
for t > 0.
c. Plot the collector current as a function of time for t > 0.
t = 0 RB
10 V
R
L = 1
k
Ω
10 V
