GATE 1988 ECE Analog Circuits (Analog Electronics) - Video Solutions

1. The OP-AMP shown in figure below is ideal and R = (L/C)1/2. The phase angle between Vo and Vi at ω = 1/(LC)1/2 is

a. π/2
b. π
c. 3π/2
d. 2π

Answer: C
Solution :

2. The quiescent collector current IC, of a transistor is increased by changing resistances. As a result
a. gm will not be effected
b. gm will decrease
c. gm will increase
d. gm will increase or decrease depending upon bias stability

Answer: C
Solution :

3. Each transistor in the Darlington pair shown below has hFE = 100. The overall hFE of the composite transistor, neglecting the leakage currents is

a. 10000
b. 10001
c. 10100
d. 10200

Answer: C
Solution :

4. The amplifier circuit shown below uses a composite transistor of a MOSFET and BIPOLAR in cascade. All capacitances are large. gm of the MOSFET is 2 mA/V, and hfe of the BIPOLAR is 99. The overall Transconductance gm of the composite transistor is

a. 198 mA/V
b. 9.9 mA/V
c. 4.95 mA/V
d. 1.98 mA/V

Answer: D
Solution :

5. The transistor in the amplifier shown below has following parameters: hfe = 100, hie = 2 kΩ, hre = 0, hoe = 0.05 mhos. All capacitors are very large. The output impedance is

a. 20 kΩ
b. 16 kΩ
c. 5 kΩ
d. 4 kΩ

Answer: D
Solution :

1 comment:

  1. It it not wrong solution for question 3 since you have considered Ic2 as overall Ic. It should be this case overall hfe= IC/Ib1 which is equal to hfe+hfe(1+hfe) =10200.please justify me


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