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Sheet 6

This document contains 7 problems involving calculating voltages and currents in BJT transistor circuits. Problem 1 asks to calculate resistor values RB and RC to establish a collector current of 1 mA and voltage of 1 V. Problem 2 involves calculating voltages and currents given a base current, collector voltage, and resistor value. Problem 3 asks to find unlabeled voltages and currents given some measurements. Problem 4 asks to calculate β values for two transistors. Problem 5 asks to design a circuit to establish specific current and voltage values. Problems 6 and 7 involve calculating voltages and currents in additional transistor circuits.

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Noha Elgammal
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24 views4 pages

Sheet 6

This document contains 7 problems involving calculating voltages and currents in BJT transistor circuits. Problem 1 asks to calculate resistor values RB and RC to establish a collector current of 1 mA and voltage of 1 V. Problem 2 involves calculating voltages and currents given a base current, collector voltage, and resistor value. Problem 3 asks to find unlabeled voltages and currents given some measurements. Problem 4 asks to calculate β values for two transistors. Problem 5 asks to design a circuit to establish specific current and voltage values. Problems 6 and 7 involve calculating voltages and currents in additional transistor circuits.

Uploaded by

Noha Elgammal
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Sheet 6

1. Consider an npn transistor operated in the active mode and the


transistor be connected as indicated by the equivalent circuit shown in
Fig. 1. It is required to calculate the values of RB and RC that will
establish a collector current of 1 mA and a collector-to-emitter voltage
of 1 V. The BJT is specified to have β = 125 and IS = 5* 10 –15.

Fig. 1

2. Consider the pnp large-signal model of Fig. 2 applied to a transistor


having IS = 10−13 A and β= 40. If the emitter is connected to ground, the
base is connected to a current source that pulls 20 μA out of the base
terminal, and the collector is connected to a negative supply of −10 V
via a 10-kΩ resistor, find the collector voltage, the emitter current, and
the base voltage.

Fig. 2
3. For the circuits in Fig. 3, assume that the transistors have very large β.
Some measurements have been made on these circuits, with the results
indicated in the figure. Find the values of the other labeled voltages and
currents.

Fig. 3
4. Find the value of β for each transistor.

Fig. 4
5. Design the circuit in Fig. 5 to establish a current of 1 mA in the emitter
and a voltage of -1V at the collector. The transistor vEB=0.64 V at
IE=0.1 mA, and β = 100.
Fig. 5
6. For each of the circuits shown in Fig. 6, find the emitter, base, and
collector voltages and currents. Use β= 30, but assume VBE=0.7 V
independent of current level.

(a) (b)
Fig. 6
7. For the circuit in Fig. 7. let VCC=5 V, RC=1 K and RB=20 K.
The BJT has β = 50.
Find the value of VBB that results in the transistor operating
(a) in the active mode with VC=1 V;
(b) at the edge of saturation;
(c) deep in saturation with βforced = 10.
Fig. 7

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