Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Sheet 2
Electronic circuits
Exercise 1
A common base transistor amplifier has an input resistance of 20 Ω and output resistance of 100
kΩ. The collector load is 1 kΩ. If a signal of 500 mV is applied between emitter and base, find
the voltage amplification. Assume αac to be nearly one.
Exercise 2
In a common base connection, IE = 1mA, IC = 0.95mA. Calculate the value of IB .
Exercise 3
In a common base connection, current amplification factor is 0.9. If the emitter current is 1mA,
determine the value of base current.
Exercise 4
In a common base connection, IC = 0.95 mA and IB = 0.05 mA. Find the value of α.
Exercise 5
In a common base connection, the emitter current is 1mA. If the emitter circuit is open, the
collector current is 50 μA. Find the total collector current. Given that α = 0.92.
Exercise 6
In a common base connection, α = 0.95. The voltage drop across 2 kΩ resistance
which is connected in the collector is 2V. Find the base current.
Exercise 7
For the common base circuit shown in Fig. 3, determine IC and VCB . Assume the transistor to be
of silicon.
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Fig. 3
Exercise 8
Find the value of β if (i) α = 0.9 (ii) α = 0.98 (iii) α = 0.99.
Exercise 9
Calculate IE in a transistor for which β = 50 and IB = 20 μA.
Exercise 10
Find the α rating of the transistor shown in Fig. 4. Hence determine the value of I C using both α
and β rating of the transistor.
Fig. 4
Exercise 11
For a transistor, β = 45 and voltage drop across 1kΩ which is connected in the collector circuit is
1 volt. Find the base current for common emitter connection.
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Exercise 12
A transistor is connected in common emitter (CE) configuration in which collector supply is 8 V
and the voltage drop across resistance RC connected in the collector circuit is 0.5 V. The value of
RC = 800 Ω. If α = 0.96, determine : (i) collector-emitter voltage (ii) base current.
Exercise 13
An n-p-n transistor at room temperature has its emitter disconnected. A voltage of 5 V is applied
between collector and base. With collector positive, a current of 0.2 μA flows. When the base is
disconnected and the same voltage is applied between collector and emitter, the current is found
to be 20 μA. Find α, IE and IB when collector current is 1 mA.
Exercise 14
The collector leakage current in a transistor is 300 μA in CE arrangement. If now
the transistor is connected in CB arrangement, what will be the leakage current? Given that β =
120.
Exercise 15
For a certain transistor, IB = 20 μA; IC = 2 mA and β = 80. Calculate ICBO.
Exercise 16
Using diagrams, explain the correctness of the relation ICEO = (β + 1)ICBO.
Exercise 17
Determine VCB in the transistor circuit shown in Fig. 10 (i). The transistor is of silicon and has β
= 150.
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Fig.10
Exercise 18
In a transistor, IB = 68 μA, IE = 30 mA and β = 440. Determine the α rating of the transistor. Then
determine the value of IC using both the α rating and β rating of the transistor.
Exercise 19
A transistor has the following ratings : IC =
(max) 500 mA and βmax = 300.
Determine the maximum allowable value of IB for the device.
Exercise 20
Fig. 11 shows the open circuit failures in a transistor. What will be the circuit behaviour in each
case ?
Fig. 11
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Exercise 21
For the circuit shown in Fig. 12 , draw the d.c. load line.
Fig.12
Exercise 22
In the circuit diagram shown in Fig. 14, if VCC = 12V and RC = 6 kΩ, draw the d.c. load line.
What will be the Q point if zero signal base current is 20μA and β = 50 ?
Fig.14
Exercise 23
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
In a transistor circuit, collector load is 4 kΩ whereas quiescent current (zero signal collector
current) is 1 mA. (i) What is the operating point if VCC = 10 V ? (ii) What will be the operating
point if RC = 5 kΩ ?
Exercise 24
Determine the Q point of the transistor circuit shown in Fig. 16. Also draw the d.c. load line.
Given β = 200 and VBE = 0.7V.
Fig. 16
Exercise 25
Determine the Q point of the transistor circuit shown in Fig. 18. Also draw the d.c. load line.
Given β = 100 and VBE = 0.7V.
Fig.18
Exercise 26
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
In the above example, find (i) emitter voltage w.r.t. ground (ii) base voltage w.r.t. ground (iii)
collector voltage w.r.t. ground.
Fig.20
Exercise 27
If the collector current changes from 2 mA to 3mA in a transistor when collector-
emitter voltage is increased from 2V to 10V, what is the output resistance ?
Exercise 28
A change of 200 mV in base-emitter voltage causes a change of 100 μA in the
base current. Find the input resistance of the transistor.
Exercise 29
For a single stage transistor amplifier, the collector load is R C = 2kΩ and the input resistance Ri =
1kΩ. If the current gain is 50, calculate the voltage gain of the amplifier.
Exercise 30
Find IC(sat) and VCE(cutoff) for the circuit shown in Fig. 21.
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Fig.21
Exercise 31
Determine the values of VCE(off) and IC(sat) for the circuit shown in Fig. 23.
Fig. 23
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Exercise 32
Determine whether or not the transistor in Fig. 24 is in stauration. Assume Vknee = 0.2V.
Fig.24
Exercise 33
Is the transistor in Fig. 25 operating in saturated state?
Fig.25
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Exercise 34
For the circuit in Fig. 27, find the base supply voltage ( V BB) that just puts the transistor into
saturation. Assume β = 200.
Fig.27
Exercise 35
Determine the state of the transistor in Fig. 28 for the following values of collector resistor : (i)
RC = 2 kΩ (ii) RC = 4 kΩ (iii) RC = 8 kΩ.
Fig. 28
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Exercise 36
In the circuit shown in Fig. 29, VBB is set equal to the following values:
(i) VBB = 0.5V (ii) VBB = 1.5V (iii) VBB = 3V. Determine the state of the transistor for each value
of the base supply voltage VBB.
Fig.29
Exercise 37
The maximum power dissipation of a transistor is 100mW. If VCE = 20V, what is the maximum
collector current that can be allowed without destruction of the transistor?
Exercise 38
For the circuit shown in Fig. 30, find the transistor power dissipation. Assume that β = 200.
Fig.30
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Technical and Vocational Training Corporation المؤسسة العامة للتدريب التقني و المهني
College of Technology in Tabuk الكلية التقنية بتبوك
Exercise 39
For the circuit shown in Fig. 31, find the power dissipated in the transistor. Assume β = 100.
Fig. 31
Exercise 40
The transistor in Fig.32 has the following maximum ratings : P D (max) = 800 mW ; VCE(max) =
15V ; IC(max) = 100 mA. Determine the maximum value to which VCC can be adjusted without
exceeding any rating. Which rating would be exceeded first ?
Fig.32
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