P E S I T (BSC) Course Information BE. -IIISem CS 10CS32

10CS32: Electronics Circuits.

Question Bank.

*Refer the circuit diagrams from the PDF file named Circuits.pdf

UNIT –I

1. Discuss with neat sketches, the relation of operating point of the for the transistor for the

following cases: i)Neat saturation region ii)Neat cut=off region ;iii)at the centre of active

region.-----------------------------------------------------------------------------------------------------------------8M

2. For the circuit shown(fig.1) calculate Ib,Ic,Vce,Vc,Ve,Vb,and Vbc. Assume B=100 -----------------8M

3. Explain the basic methods of triggering SCR.-----------------------------------------------------------------4M

4. With a neat figures explain the construction and operational principle of an UJT.--------------10M

5. Explain Thermal runaway with reference to the transistors.---------------------------------------------4M

6. Find the values of the resistors Rb,Rc,Re and the transistor gain B for the circuit shown the fig 4.

given that Ib=40 micro amps, Ic=4mA Ve=2V,Vce=12V and supply voltage VCC=15V.-------------5M

7. Explain the effects of collector resistor, base current and supply voltage on the operating point

of a fixed bias circuit. Which is the ideal position for an operating point on the BJT fixed bias

transistor circuit? Explain the above with neat diagrams.------------------------------------------10M

8. What is the operating point for the following voltage divider bias circuit(fig.8)?-------------------8M

UNIT –II

1. What is the difference between JFET and MOSFET? ----------------------------------------------------- 5M

2. With the help of at fig, explain the construction of N-Channel depletion MOSFET--------------10M

3. Fig.5 shows a biasing configuration using DE-MOSFET. Given that the saturation drain current is

8mA. And the pinch off voltage is -2V.Determine the value of gate-source voltage, drain current

and the drain voltage.---------------------------------------------------------------------------------------------5M

4. Explain with neat sketches, the operation of JFET along with its characteristics curve----------8M

5. Discuss merits, demerits and applications of IGBT’s-------------------------------------------------------7M

6. Explain the working of N-channel E-MOSFET with neat diagram. Explain the output

Characteristics of the same.-------------------------------------------------------------------------------------10M

7. Find the values of voltages Vd and Vc for the circuit shown(Fig.9).Assume β=100.Vbe=0.7v,

Saturation drain current of JFET is-10ma and pinch off voltage is -5V.----------------------------10M

UNIT –III

1. Discuss the classification of the optoelectronic devices in detail----------------------------------------6M

2. Explain with neat sketches the principle of operation of JFET along with its characteristics,

advantages, disadvantages and applications of photodiode-------------------------------------------8M

3. Briefly discuss with the necessary diagrams the basic operation and construction of LED. ------6M

P E S I T (BSC) Course Information BE. -IIISem CS 10CS32

4. Define the following terms i)responsivity (R) ii) Noise Equivalent power(NEP)iii)Directivity,

iv)Quantum efficiency V)response time.-------------------------------------------------------------5M

5. What is phototransistor? Draw the schematic symbol of phototransistor. Explain VI

characteristics of phototransistor. ----------------------------------------------------------------------------5M

6. Explain different modes of operation of LCD display------------------------------------------------10M

7. Explain photodiode, phorosensor, photoconductor and photo transistors with necessary

diagrams.----------------------------------------------------------------------------------------------------------10M

8. Find the value of RL for the circuit shown in (fig.10). such that the circuit gives a logic high when

the light incident on it is above 200 lux and the photoconductor has the resistance of 14KΩ at a

light level of 100 lux, α=0.5,power supply voltage is Vcc=10V And reference voltage of zener

diode is 3.5V----------------------------------------------------------------------------------------------------10M

9. A photo diode has a noise current of 1*10-15

A,responsivity of 0.5 A/W,active area of 1mm2 and

rise time of 3.5ns.Determine its i)NEP;ii)Detectivity;iii)D*;iv)Quantum efficiency at 850nm.---4M

UNIT –IV

1. Draw the generalized H-Parameter model of the transistor based amplifier and derive the

expression for: i)current gain ii)input impedance iii)Voltage gain iv)output admittance.------10M

2. With a neat fig, explain the operation of Darlington amplifier.---------------------------------------5M

3. What are cascade amplifiers? What are the advantages offered by cascade amplifiers? --------5M

4. Explain common emitter, common collector amplifier along with its a.c. equivalent circuit.----4M

5. In the common collector shown in fig 2. the transistor parameters hie = 1.2k, hfe=-101,hre=1

and hoe=25 micro ampere/v. Calculate Ri, Ai, Av, and Ro for the circuit.------------------------- 8M

6. Graphically how h-parameters of a BJT are determined? Explain with a neat diagram. Also derive

expression for input impedance and voltage gain for BJT amplifiers.---------------------------------10M

7. Given a hybrid equivalent circuit shown, in Fig. (12 ) find input impedance, voltage gain ,current

gain and output impedance. The h-parameters are hie=1.5k,hfe=100,hre=1*10 -4

,hoe=25µA/v --

-------------------------------------------------------------------------------------------------------------------------10M

UNIT –V

1. Explain the classification of the large signal amplifiers as class-A,class B,class C and class AB

amplifiers.---------------------------------------------------------------------------------------------------------6M

2. An amplifier with openloop voltage gain of 1000W,delivers 10 W of power output at 10% second

harmonic distortion when input is 10mv. A 40dB negative feedback is applied and output power

is to remain at 10W.Determine required input signal Vs and second harmonic distortion with

feedback.--------------------------------------------------------------------------------------------------------------8M

3. Explain the advantages and disadvantages of negative feedback-------------------------------------6M.

4. What are the advantages of negative feedback?----------------------------------------------------------5M

5. Derive the relevant expressions to prove that input resistance increases and output resistance

reduces in case of voltage series feedback-------------------------------------------------------------------8M

6. Refer to the fig.(6) of opamp based inverting amplifier circuit. Identify the type of negative

feedback. Determine the trans impedance gain, the input impedance gain, the input impedance

P E S I T (BSC) Course Information BE. -IIISem CS 10CS32

and output impedance of the amplifier. given that transimpedance, input impedance and output

impedance parameters of the op-amp are 100MΩ,10MΩ and 100Ω respectively .--------------7M

7. Discuss large signal amplifier characteristics. Discuss Harmonic distortion .Derive

A0,A1,A2,A3,A4, the amplitude of DC,first, second, third, fourth amplitude of harmonic

components.--------------------------------------------------------------------------------------------------------10M

8. Derive expressions for gain, input resistance, and output resistance of voltage shunt feedback

amplifier with a help of a neat diagram. For the op-amp based inverting amplifier circuit shown

in fig (11 ) Find input impedance, given the transimpedance, input impedance and output

impedance of op-amp are,100MΩ,10MΩ and 100Ω respectively.-----------------------------------10M

UNIT –VI

1. Explain the Bark Hausen criteria as referred oscillators.--------------------------------------------5M

2. Explain Voltage controlled oscillator --------------------------------------------------------------------7M

3. With a neat fig. and relevant waveform explain the operation of astable multivibrator using

IC555 timer.---------------------------------------------------------------------------------------------------10M

4. Explain with a neat diagram Hartley oscillator and colpits oscillator as LC oscillator.--------6M

5. Explain various types of mutivibators. Also mention the applications---------------------------6M

6. Obtain the expression for the time period T at the base of the transistor in case of wave

shaping circuits.------------------------------------------------------------------------------------------------8M

7. Mention the conditions necessary for oscillations in feedback amplifier circuit. Determine

the frequency at which the following circuit shown in fig(13 ) would oscillate if the loop gain

criteria was met. Also determine the max, value of R1. For sustained oscillations.-------10M

8. With a neat diagram and waveforms explain the working of bistable multivibrator.-----10M

9. For a darlington amplifier,two transistors Q1 and Q2 are identical and the h-parameters for

both the transistors are hie=1KΩ hfe=100 and hoe=40*10-6 mhos.The values of voltages

Vcc=15V,Vbe1=0.7V and vbe2=0.7v.Determine i)input impedence, ii)output impedence;

iii)Voltage gain;iv)current gain.-------------------------------------------------------------------8M

UNIT –VII

1. Name the constituent parts of a basic linearly regulated power supply. Briefly describe the

function of each of the constituent parts.-------------------------------------------------------------5M

2. Define: i)Load regulation ii)Line regulation iii)Ripple rejection factor with reference to the

regulated power supplies. -------------------------------------------------------------------------5M

3. With a neat fig. explain the working of buck regulator.----------------------------------------7M

4. Refer to the regulator ckt. shown in fig.7. Determine: i)Load current, ii)Current through

LM7812 iii)Current through external transistors. iv)Power dissipated in LM7812. Take Vbe

=0.7V---------------------------------------------------------------------------------------------------5M

5. Explain with a functional block diagram a typical three terminal IC voltage regulator------6M

6. Discuss the limitations of the linear voltage regulators----------------------------------------6M

7. Briefly discuss power converters in series and parallel connection along with neat diagrams.

P E S I T (BSC) Course Information BE. -IIISem CS 10CS32

-----------------------8M

8. Determine the output ripple of regulated power supply which provides a ripple rejection of

80dB and a ripple voltage in a unregulated input were 2V -----------------------------------10M

9. Explain boost regulator and inverting regulator with neat diagram-------------------------10M

10. Design a power transformer with a multi output secondary and the following input /output

Specifications.i)Primary voltage:220V,50HZ ii)Secondary voltage: a) 12-0-12 V at 100mA

b)15V at1A.Assume B=60000 lines per square inch and efficiency of 90%.------------------6M

UNIT –VIII

1. Discuss the requirements of the good instrumentation amplifier --------------------------------6M

2. Fig.3. shows dual input balanced output and differential amplifier configuration. Assuming Si

transistor, with hie=2.8KΩ, calculate i)Operating point the valves; ii)Differential gain

iii)common mode gain iv)CMRR v)Output if Vs1=70mV peak to peak at 1kHz; vi)Vs2=40mV

peak to peak at 1kHz.--------------------------------------------------------------------------------10M

3. Explain the various electrical characteristics of an op-amp which are generally in the data

sheet.----------------------------------------------------------------------------------------------------------4M

4. Define the following as referred to op-amp i)CMRR ii)PSRR iii)Slew rate iv)Bandwidth v)Open

loop gain-------------------------------------------------------------------------------------------------5M

5. With a neat fig. Explain the operation of the peak detector circuit using op-amp-----------7M

6. With a neat fig. and relevant waveforms explain the working of the relaxation oscillator

circuit using op-amp.----------------------------------------------------------------------------------8M

7. Explain absolute value circuit and its working.----------------------------------------------------10M

8. Explain with a neat diagram i)Current to voltage converter ii) Voltage to current converter

and its working.---------------------------------------------------------------------------------------10M

9. List and explain the performance parameters of operational amplifiers.--------------------8M

P E S I T (BSC) Course Information BE. -IIISem CS 10CS32