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DEPARTMENT OF ELECTRICAL ENGINEERING, IIT KANPUR

EE210: Microelectronics - I HW – 4

Unless stated otherwise, the BJT in the problems given below has the following characteristics Q.1 Two amplifiers A and B have the following characteristics:

2Amp-A : 10 ; 1 ; 1VO in oA R k R k ; Amp-B : 10; 100 ; 100VO in oA R k R

Create two examples, one where A gives higher voltage gain and another where B provides a higher voltage gain Q.2 An amplifier’s input-output relationship is described by the equation:

21 2( )o inv K v K . Determine expression for second harmonic distortion.

Assuming input is a sinusoid, determine maximum output voltage swing such that harmonic distortion is less than 5% for K2 = 1V and K1=5. Q.3 The amplifier given below in Fig. 1 has a maximum output current drive capability of 1mA. Sketch qualitatively the output when the magnitude of sinusoidal input is 5mV and when it is 20mV.

Fig. 1 Fig. 2 Q.4 (a) For the amplifier circuit shown in Fig. 2, determine suitable values for emitter and collector resistance so that the bias point or (Q-point) is

1 ; 3.7CQ CEQI mA V V .

(b) Using small signal analysis, determine the mid-frequency voltage gain.

152.03 10 ; 100; 1; 100; 200 ; 26

1 ; 0.5 ; 3 ; 0.5; 0.85; 1S F R A bb T

jeo jco jso bi F

I A V r V mV

C pF C pF C pF m V ns

vo

vs

RE

-5V

2K

RC

5V

RL

1k

Vin

Avo=100Rin =1kRo=10

2

(c) suggest a method for increasing the dc collector-emitter voltage to 5.7CEQV V while keeping collector current, supply voltages and voltage gain

unchanged. What is the resulting disadvantage? Q.5 What will be the voltage gain of the amplifier shown below? Modify the circuit suitably so that it provides voltage gain.

5V

vs

vo

180K2.5K

2.5K