Amity University Haryana

Amity School of Engineering and Technology

Department of Electronics and Communication Engineering

Tutorial Sheet 1

1. The conductivity of intrinsic Si is 3 s/m at room temperature and the electron and

hole mobilities in it are 0.4 m2/V.Sec and 0.2 m

2/V.Sec respectively. Calculate the

number of electrons and holes per m3 participating in the conduction process.

2. Show that the maximum rectification efficiency of HWR is 40.6% and that of FWR is

81.2%

3. A full wave rectifier circuit uses two silicon diodes with a forward resistance of 20Ω

each. A DC voltmeter connected across the load of 1kΩ reads 55.4volts. Calculate

a. IRMS

b. Average voltage across each diode

c. ripple factor

d. Transformer secondary voltage rating.

4. The voltage across a Si diode at room temperature of 3000k is 0.71V when 2.5mA

current flows through it. If the voltage increases to 0.8V, calculate the new diode

current.

5. Find the conductivity of intrinsic silicon at 3000

K. It is given that ni at 3000

K in

silicon is 1.5X1010

/cm3 and the mobilities of electrons and holes in silicon are

1300cm2/V-s and 500 cm2/V-s respectively.

a. If donor type impurity is added to the extent of 1 impurity atom in 108 silicon

atoms find the conductivity.

b. If acceptor type impurity is added to the extent of 1 impurity atom in 108

silicon atoms find the conductivity.

6. A specimen of silicon is 0.2 mm long and has a cross-section of 0.2x0.2 mm. One

volt impressed across the bar results in a current of 8 mA. Assuming that the current

is due to electrons, calculate:

a. Concentration of free electrons, and

b. Drift velocity

Given that at 3000 K mobilities of electrons is1300 cm2/V-s.

7. A potential difference if 10 V is applied longitudinally to a rectangular specimen of

intrinsic germanium of length 25mm, width 4 mm and thickness 1.5mm. Determine at

room temperature:

a. Electron and hole drift velocities

b. The conductivity of intrinsic germanium if intrinsic carrier density is 2.5x1019

/m3 and

c. The total current

8. A bridge rectifier is used to supply d.c. load of 20A at 20V from 117V source. What

are the ratings of power transformer?

9. For silicon the intrinsic concentration is approximately 1016

carriers/m3. If an impurity

concentration of 1022

donor atoms/m3 is doped, determine the electron and hole

concentration. .

Amity University Haryana

Amity School of Engineering and Technology

Department of Electronics and Communication Engineering

Tutorial Sheet 2

1. Find the value of β if α = 0.98 for a transistor.

2. A BJT with β= 49 and ICO = ICBO = 1 µA and IB = 10µA. Calculate IC?

3. An emitter follower using p-n-p transistor with β0 = 150 is biased at IC = 0.25 mA.

The voltage signal source has RS = 3kΩ:

a. In order to make overall R0 = 110Ω determine RE.

b. For this value of RE obtain AV and input resistance.

4. In the fixed bias circuit of a transistor VCC = 15V, RB = 300k Ω, RL = 2kΩ. If β = 100,

ICO = 20nA and VBE = 0.7V. Find the stability factor of Q-point with respect to ICO.

5. Potential divider biasing from VCC = 15 volts is obtained for an n-p-n transistor.

Given R1 = 72kΩ, R2 = 18kΩ, RE = 1.4kΩ, RC = 4kΩ. Determine the operating point:

a. When β = 125

b. When β is doubled

c. Use VBE = 0.7V and comment on stability of operating point with change in β.

6. The h-parameters of a transistor used in a CE circuit are hie = 1.0 KΩ , hre =

10×10−4, hfe = 50, hoe = 100 K. The load resistance for the transistor is1 KΩ in the

collector circuit. Determine Ri, Ro, AV ,AI in the amplifier stage (Assume RS =

1000Ω ).

Amity University Haryana

Amity School of Engineering and Technology

Department of Electronics and Communication Engineering

Tutorial Sheet 3

1. In a CE transistor amplifier when signal changes by 0.02V, the base current changes

by 10µA and collector current by 1 mA. If the collector resistance RC = 5kΩ and RL =

10kΩ, find;

a. Voltage gain

b. Current gain

c. Input impedance

d. AC load resistance, and

e. Power gain

2. In the circuit shown, if IC=2mA and VCE=3V. Calculate R1 and R3.

3. For the CE amplifier circuit shown below, find the percentage change in collector

current if the transistor with hfe=50 is replaced by another transistor with hfe=150.

Assume VBE=0.6V (figure 4)

4. If the various parameters of a CE amplifier which uses the self bias method are VCC =

12 V, R1 = 10 kΩ, R2 = 5kΩ, RC 1kΩ, Re =2 KΩ and β = 100, find

a. The coordinates of the operating point, and

b. The stability factor, assuming the transistor to be of silicon.

5. Calculate the values of IE, βdc and αdc for a transistor with IC=12.427µA, IB=200mA,

ICBO=7µA. Also determine the new level of IC which will result from reducing IB to

150µA.

6. In the CE amplifier of self biasing IE = 1 mA, RE = 1000Ω and β = 49. Find the value

of R1 and R2 such that the stability factor does not exceed 5. Assume VCC = 5V and

VBE = 0.

Amity University Haryana

Amity School of Engineering and Technology

Department of Electronics and Communication Engineering

Tutorial Sheet 4

1. For an N-channel JFET drain current with gate shorted: 8.7 mA pinch off voltage is -

1V. Find the value of a. Drain current. b. Transconductance

2. For the circuit shown below, find the values of VDS and VGS. Given ID=5mA,

VDD=10V, RD=1KΩ, RS=500Ω.

3. A JFET has VP = - 4.5 V, IDSS = 10 mA and IDS = 2.5 mA. Determine the

transconductance.

4. A self-biased n-channel JFET has a VD = 6 V. VGS = –3 V. Find the value of VDS.

5. Refer to figure sh1own below. Determine the value of VS and VDS.

6. Refer to the given figure. ID = 6 mA. Calculate the value of VDS.

7. With a 30-volt VDD, and an 8-kilohm drain resistor, what is the E-MOSFET Q point

voltage, with ID = 3 mA?

8. A JFET data sheet specifies VGS(off) = –6 V and IDSS = 8 mA. Find the value of ID

when VGS = –3 V.

9. Refer to this figure. Find the value of VD.

10. Refer to this figure. The voltage gain is

Amity University Haryana

Amity School of Engineering and Technology

Department of Electronics and Communication Engineering

Tutorial Sheet 5

1. The open-loop gain of an amplifier is -200. A voltage series negative feedback is used

with a feedback ratio of -0.02.The input and output impedances of the amplifier are

2kΩ and 40kΩ respectively in the absence of feedback. Determine the closed-loop

gain, input and output impedances when the feedback circuit is completed.

2. The gain and distortion of the amplifier are 150 and 5% without feedback. If 10% of

its output voltage applied is fed back as negative feedback, find the distortion of the

amplifier with feedback.

3. An Amplifier has a voltage gain of 400, f1=50Hz, f2 = 200 KHz and a distortion of

10% without feedback. Determine the voltage gain, f1f, f2f and Df when a negative

feedback is applied with feedback ratio of 0.001.

4. The gain of an amplifier is decreased to 1000 with negative feedback from its gain of

5000. Calculate the feedback factor and the amount of negative feedback in dB.

5. In the base bias with collector and emitter feedback circuit, VCC = 24V, RL = 10kΩ

and RE = 270Ω. If the silicon transistor is used with β = 45 and if under quiescent

conditions VCE = 5V determine RB and stability factor.