# Test: Differential Amplifiers

## 10 Questions MCQ Test Topicwise Question Bank for Electronics Engineering | Test: Differential Amplifiers

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Attempt Test: Differential Amplifiers | 10 questions in 30 minutes | Mock test for Electronics and Communication Engineering (ECE) preparation | Free important questions MCQ to study Topicwise Question Bank for Electronics Engineering for Electronics and Communication Engineering (ECE) Exam | Download free PDF with solutions
QUESTION: 1

Solution:

QUESTION: 2

### In the level shifter circuit shown in figure beiow, the internal drop across each diode VD = VBE2 = 0.7 V and hfe is very large. The value of R for V0 to become zero is

Solution:

The aiven circuit is redrawn as shown below.

Writing loop equation containing two diodes and

QUESTION: 3

### A differential amplifier, amplifies

Solution:

The goal of designing differential amplifiers is to minimize the effect of common-mode input signal and amplify the difference of the voltages between the two input lines.

QUESTION: 4

Most of linear ICs are based on the two transistor differential amplifier because of its

Solution:
QUESTION: 5

A differential amplifier has RL = 10 kΩ(equal values in both collectors), hie = 1 kΩ, Re = 50 kΩ, hte = 100. The common mode gain is given by

Solution:

Common- mode gain,

QUESTION: 6

In a single-stage differential amplifier, the output offset voltage is basically dependent on the mismatch of

Solution:

In single stage differential amplifier, the output offset voltage is basically dependent on the mismatch of IB and β.

QUESTION: 7

Assertion (A): It is not so easy to design d.c. amplifiers using transistors.
Reason (R): The values of hfe ,VBE and ICBO vary with temperature.

Solution:

The values of hFE, VBE and ICB0 vary with temperature and due to the variation in any of these quantities the output voltage may change which may not be distinguished from a change in the input signal voltage, Due to this reason it is not so easy to design d.c. amplifiers using transistors. Hence, both assertion and reason are true and reason is the correct explanation of assertion.

QUESTION: 8

Assertion (A): The ability of a differential amplifier to reject a differential mode signal is called its “figure of merit”.
Reason (R): The ideal value of figure of merit of a differential amplifier is infinite.

Solution:

Assertion is not true because “figure of merit” (or CM MR) of a differential amplifier is to reject a common mode signal (vC).

QUESTION: 9

A differential amplifier has (i) CMMR= 1000 and (ii) CMRR= 10000.
The first set of inputs is V1= 100 μV and V2, = -100μV.
The second set of inputs is V1= 1100 μV and V2 = 900 μV.
What is the percentage difference in output voltage obtained for the two sets of input voltages?

Solution:

we know that

Now,

From equation (iii) and (iv), the percentage difference in output voltage obtained for the two sets of input voltages

QUESTION: 10

The Q-point (Vc and IB) for the differential amplifier shown in figure below is given by:

Solution:

Also

Hence, both transistors of the differential amplifier are biased at a Q-point having lB = 1.09 μA and Vc=7.9V.

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