The input impedance of op-amp circuit of figure is 120 k ohm 110 k ohm infinity

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Question
The input impedance of op-amp circuit of figure is
Options
A. 120 k ohm
B. 110 k ohm
C. infinity
D. 10 k ohm

Correct Answer

10 k ohm

Explanation

Due to the presence of virtual ground at input, the resistance in the series path of input of inverting amplifier is input impedance.

Analog Electronics problems

Search Results

1. For a system to work, as oscillator the total phase shift of the loop gain must be equal to
Options
A. 90�
B. 45�
C. 270�
D. 360�

2. If the input to the ideal comparator shown in the figure is a sinusoidal signal of 8 V (peak to peak) without any DC component, then the output of the comparator has a duty cycle of
Options
A. 1/2
B. 1/3
C. 1/6
D. 1/12

3. The transistor of following figure in Si diode with a base current of 40 ?A and I_CBO = 0, if V_BB = 6V, R_E = 2 k? and ? = 90, I_BQ = 20 ?A then R_B =
Options
A. 200 k?
B. 265 k?
C. 150 k?
D. 100 k?

4. The efficiency of a full wave rectifier using centre tapped transformer is twice that in full wave bridge rectifier.
Options
A. True
B. False

5. A half wave diode rectifier has a capacitance input filter. If input voltage is V_m sin ?t, PIV is
Options
A. V_m
B. 2 V_m
C. 3 V_m
D. 4 V_m

6. An RC coupled amplifier has an open loop gain of 200 and a lower cutoff frequency of 50 Hz. If negative feedback with ? = 0.1 is used, the lower cut off frequency will be
Options
A. about 50 Hz
B. about 5 Hz
C. about 2.38 Hz
D. about 70.5 Hz

7. For a base current of 10 ?A, what is the value of collector current in common emitter if ?_dc = 100
Options
A. 10 ?A
B. 100 ?A
C. 1 mA
D. 10 mA

8. Assertion (A): CE amplifier is the most widely used BJT amplifier
Reason (R): CE amplifier has zero phase difference between input and output
Options
A. Both A and R are correct and R is correct explanation for A
B. Both A and R are correct but R is not correct explanation for A
C. A is correct R is wrong
D. A is wrong R is correct

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