GATE 2008 ECE Video Solutions on Analog Circuits (Analog Electronics)

1. Consider the following circuit using an ideal OP-AMP. The I-V characteristic of the diode is described by the relation I = I_{o}(exp(V/V_{T}) - 1), where VT = 25 mV, I_{o} = 1 µA and V is the voltage across the diode(taken as positive for forward bias). For an input voltage V_{i} = - 1 volts, the output voltage V_{o} is

3. Consider the schmitt trigger circuit shown below.

A triangular wave which goes from –12 volts to +12 volts is applied to the inverting input of OP-AMP. Assume that the output of the OP-AMP swings from +15 volts to –15 volts. The voltage at the non-inverting input switches between
a. – 12 volts and +12 volts
b. – 7.5 volts and +7.5 volts
c. – 5 volts and +5 volts
d. 0 volts and +5 volts

Statement for Linked Answer Question:
In the following transistor circuit, V_{BE} = 0.7 volts, r_{e} = 25 mV/I_{E}, β and all the capacitances are very large.

4. The value of DC current I_{E} is
a. 1 mA
b. 2 mA
c. 5 mA
d. 10 mA

Answer:A

5. The mid-band voltage gain of the amplifier is approximately
a. – 180
b. – 120
c. – 90
d. – 60