# Analog Electronics - 7

## 10 Questions MCQ Test RRB JE for Electronics & Communication Engineering | Analog Electronics - 7

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Attempt Analog Electronics - 7 | 10 questions in 30 minutes | Mock test for Electronics and Communication Engineering (ECE) preparation | Free important questions MCQ to study RRB JE for Electronics & Communication Engineering for Electronics and Communication Engineering (ECE) Exam | Download free PDF with solutions
QUESTION: 1

### For the Wien-bridge oscillator circuit shown below, the condition for bridge balance is

Solution:

At oscillator frequency
i.e. gain of non-inverting amplifier
⇒ RB = 2RA

QUESTION: 2

### Find the value of inductance in (mH) in the oscillator shown below to achieve a frequency of oscillation = 100 KHz is

Solution:

*Answer can only contain numeric values
QUESTION: 3

### For the circuit shown in the figure the value of R to get oscillation of 100 kHz is ________ KΩ.

Solution:

The given oscillator is Colpitts’s oscillator

The condition for oscillation is

|Aβ|=1

A = -R2/R1

β=C2/C1

*Answer can only contain numeric values
QUESTION: 4

The figure shows a phase-shift oscillator circuit with voltage follower buffer stages.

The value of R2/R required for sustained oscillations is _____.

Solution:
• The basic amplifier of the circuit is the op-amp A3.
• The output of amplifier is connected to 3 stage RC filter.

Transfer function of first RC network

The amplifier A3 is connected in inverting mode

The loop gain is

Substitute real part of denominator to zero

At this frequency

QUESTION: 5

The value of R in oscillator circuit shown in a given circuit below is chosen such that it oscillates at an angular frequency of ω. The value of ω and the required value of R will respectively be

Solution:

Hartley oscillator

Amp with +ve F.B

Loop again AB = 1 + j0

At oscillation

∠AB = 0 (no reactance XL = XC)

At frequency of oscillation look lies resistive Network

For ideal op amp

Use voltage division Rule

R + 1 = 21

R = 20 kΩ

R = 2 × 104Ω

*Answer can only contain numeric values
QUESTION: 6

The frequency of oscillation of the circuit in kilohertz is ______ kHz.

Solution:

The given circuit is wein bridge oscillator.

R3 = R4 = 159 KΩ

C1 = C2 = 1 nF

= 103 HZ

= 1 KHZ

QUESTION: 7

For the transistor oscillator circuit given below the frequency of oscillation is 8.5 kHz. The value of the collector resistor approximately is

Solution:

In a transistor phase shift oscillator the oscillation frequency

R, C are the resistor and the capacitor in phase shift circuit

RC is collector capacitance

⇒ RC = 2R = 10 kΩ

*Answer can only contain numeric values
QUESTION: 8

The oscillation frequency if the below-shown oscillator is 1 kHz then the value of ‘L’ is ______ mH

Solution:

The given oscillator is Hartley oscillator, where the oscillation frequency.

= 253.3 mH

Leq = L + 5 mA

⇒ L = 253.3 – 5

= 248. 3 mH

QUESTION: 9

For the circuit shown the value of R1 and R2 such that the circuit generates oscillations of frequency 274 Hz is [Assume the time constant of the feedback RC network is 0.01 sec]

Solution:

Given figure is of A-stable multi-vibrator,

Time constant is given by

β = feedback factor

τ = time constant of feedback loop:

Option 3 satisfies the condition

*Answer can only contain numeric values
QUESTION: 10

The frequency of oscillation of the circuit shown below is ________ Hz.

Solution:

The given oscillator is Wien-bridge oscillator with R = 5 kΩ, C = 1 μF

⇒ frequency of oscillation f = 1/2πRC

= 31.8 Hz

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