# Analog Circuits (Test 4)

## Gate Exam : Ec Electronics And Communication Engineering

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Analog Circuits
| Analog Circuits |
Q.1
The nature of feedback in the op-amp circuit shown is

A. Current - Current feedback
B. Voltage - Voltage feedback
C. Current - Voltage feedback
D. Voltage - Current feedback
Explaination / Solution:
No Explaination.

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Q.2
The following circuit has R = 10kΩ, C = 10μF . The input voltage is a sinusoid at 50Hz with an rms value of 10V. Under ideal conditions, the current is from the source is

A. 10 π mA leading by 90°
B. 10 π mA leading by 90°
C. 20 π mA leading by 90°
D. 10 π mA lagging by 90°
Explaination / Solution:
No Explaination.

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Q.3
Consider the oscillator circuit shown in the figure. The function of the network (shown in dotted lines) consisting of the 100kΩ resistor in series with the two diodes connected back-toback is to:

A. Introduce amplitude stabilization by preventing the op amp from saturating and thus producing sinusoidal oscillations of fixed amplitude
B. Introduce amplitude stabilization by forcing the op-amp to swing between positive and negative saturation and thus producing square wave oscillations of fixed amplitude
C. Introduce frequency stabilization by forcing the circuit to oscillate at a single frequency
D. Enable the loop gain to take on a value that produces square wave oscillations
Explaination / Solution:

When the output voltage is positive the diode D1 is turned on making 100kΩ resistor to become parallel to 22.1kΩ. So the gain is reduced. When the output voltage becomes negative the diode D2 is turned on thereby again 100kΩ resistor to become parallel to 22.1kΩ. So the gain is reduced. With the use of diodes, the non ideal OP-Amp is made stable to produce steady

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Q.4
For the operational amplifier circuit shown, the output saturation voltages are ± 15V. The upper and lower threshold voltages for the circuit are, respectively.

A. + 5V and - 5V
B. + 7V and - 3V
C. + 3V and - 7V
D. + 3V and - 3V
Explaination / Solution:

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Q.5
In a transconductance amplifier, it is desirable to have
A. a large input resistance and a large output resistance
B. a large input resistance and a small output resistance
C. a small input resistance and a large output resistance
D. a small input resistance and a small output resistance
Explaination / Solution:

In the transconductance amplifier it is desirable to have large input resistance and large output resistance.

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Q.6
The filters F1 and F2 having characteristics as shown in Figures (a) and (b) are connected as shown in Figure (c).

The cut-off frequencies of F1 and F2 are f1 and f2 respectively. If f1 < fthe resultant circuit exhibits the characteristics of a

A. Band-pass filter
B. Band-stop filter
C. All pass filter
D. High-Q filter
Explaination / Solution:
No Explaination.

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Q.7
In the circuit shown below the op-amps are ideal. Then, Vout in Volts is

A. 4
B. 6
C. 8
D. 10