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If the feedback voltage and the output voltage are given as 10v and 4v. Find the gain of the feedback circuit in voltage-series feedback amplifier?
A
2.5v
B
40v
C
3v
D
6.2v
Correct Answer:
2.5v
Gain of feedback, B = Vf /Vo = 10v/4v = 2.5v.
An amplifier of gain 1000 is made into a feedback amplifier by feeding 9.9% of its output voltage in series with the input opposing. If f
L
= 20 Hz and f
H
= 200 kHz for the amplifier without feedback, then due to the feedback
A
the gain decreases by 10 times
B
the output resistance increases by 10 times
C
the f<sub>H</sub> increases by 100 times
D
the input resistance decreases by 100 times
An amplifier without feedback has a voltage gain of 50, input resistance of 1 kΩ & Output resistance of 2.5 kΩ.The input resistance of the current shunt negative feedback amplifier using the above amplifier with a feedback factor of 0.2 is
A
$$\frac{1}{{11}}{\text{k}}\Omega $$
B
$$\frac{1}{5}{\text{k}}\Omega $$
C
5 kΩ
D
11 kΩ
For the given circuit, what is the minimum peak value of the output waveform if the input waveform is 10V square wave with switching time of 1 second? Assume that the input switches between +10V and -10V DC levels.
A
0 V
B
-5 V
C
-20 V
D
-10 V
Write the formula for closed loop voltage gain of inverting amplifier with feedback using open loop voltage gain and gain of feedback circuit.
A
AF= A/(1+AB)
B
AF= -A/(1+AB)
C
AF= -B/(1+AB)
D
None of the mentioned
The ratio of the short circuit current gain of a current amplifier (Ai) to the open circuit voltage gain of a voltage amplifier (AV), given that both amplifiers have the same value of the input resistance (Ri) and output resistance (R0), is
A
Ri
B
Ro
C
Ri / R0
D
Ro / Ri
The gain of the differential amplifier is -125. Assume the voltage applied to bridge circuit Vdc=+10v and the unstrained resistance of four element of strain gage is 200Ω. When a certain weight is placed on the platform, the output voltage Vo=5v. Determine the change in resistance of each strain gage for analog weight scale. (Assuming the output is initially nulled).
A
1Ω
B
0.8Ω
If source resistance in an amplifier circuit is zero, then voltage gain (output to input voltage ratio) and source voltage gain (output to source voltage ratio) are the same.
A
True
B
False
While performing an experiment to determine the gain for an ideal operational amplifier having finite gain, a student mistakenly used the equation 1 + R2/R1 where R2 is the feedback resistance. What is the percentage error in his result? Given A is the finite voltage gain of the ideal amplifier used.
A
(R2/R1)/(A+ R2/R1) X 100%
B
(1+R2/R1)/(A+R2/R1) X 100%
C
(1+R2/R1)/(A+1+R2/R1) X 100%
D
(R2/R1)/(A+1+R2/R1) X 100%
A certain inverting amplifier has a closed-loop voltage gain of 25. The OP-amp has an open-loop voltage gain of 100,000. If an OP-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain
A
doubles
B
drops to 12.5
C
remains at 25
D
increases slightly
Consider a voltage series feedback network, where amplifier gain = 100, feedback factor = 5. For the basic amplifier, input voltage = 4V, input current=2mA. Find the input resistance of the network.
A
1.002kΩ
B
1002kΩ
C
2kΩ
D
2000kΩ