Study resources on Kenyaplex

Get ready-made curriculum aligned revision materials

Exam papers, notes, holiday assignments and topical questions – all aligned to the Kenyan curriculum.

Or go directly to:

Class notes Holiday assignments Topical questions Other resources

Explain the Barkhausen Criterion

Answers

- Barkhausen criterion is that in order to produce continuous undamped oscillations at the output of an amplifier, the positive feedback should be such that:
m_vA_v = 1
- Once this condition is set in the positive feedback amplifier, continuous undamped oscillations can be obtained at the output immediately after connecting the necessary power supplies.

(i) Mathematical explanation: The voltage gain of a positive feedback amplifier is given by;

- We know that we cannot achieve infinite gain in an amplifier. So what does this result infer in physical terms? It means that a vanishing small input voltage would give rise to finite (i.e., a definite amount of) output voltage even when the input signal is zero. Thus once the circuit receives the input trigger, it would become an oscillator, generating oscillations with no external signal source.

(ii) Graphical Explanation. Let us discuss the condition m_vA_v = 1 graphically.

Wilfykil answered the question on August 15, 2019 at 12:30

Answer Attachments

Next: 1600cm³ of fresh water of density 1g/cm³ are mixed with 1400cm³ of sea water of density 1.25g/cm³. Determine the density of the mixture.

Previous: Correct the error in the following sentences.

View more Electronics Questions and Answers | Return to Questions Index

Exams With Marking Schemes

Related Questions

Give the Essentials of Transistor Oscillator (Solved)

Give the Essentials of Transistor Oscillator

Date posted: August 15, 2019 . Answers (1)
What is a Positive Feedback Amplifier — Oscillator? (Solved)

What is a Positive Feedback Amplifier — Oscillator?

Date posted: August 15, 2019 . Answers (1)
Explain and show Undamped Oscillations from Tank Circuit (Solved)

Explain and show Undamped Oscillations from Tank Circuit

Date posted: August 15, 2019 . Answers (1)
What is an Oscillatory Circuit? (Solved)

What is an Oscillatory Circuit?

Date posted: August 15, 2019 . Answers (1)
List and explain the various types of Sinusoidal Oscillations (Solved)

List and explain the various types of Sinusoidal Oscillations

Date posted: August 15, 2019 . Answers (1)
Give the advantages of a sinusoidal oscillator (Solved)

Give the advantages of a sinusoidal oscillator

Date posted: August 15, 2019 . Answers (1)
What is a Sinusoidal Oscillator? (Solved)

What is a Sinusoidal Oscillator?

Date posted: August 15, 2019 . Answers (1)
Define the term Phase Reversal (Solved)

Define the term Phase Reversal

Date posted: August 15, 2019 . Answers (1)
Select a suitable value for the emitter bypass capacitor in Fig. 5.4 if the amplifier is to operate over a frequency range from 2 kHz... (Solved)

Select a suitable value for the emitter bypass capacitor in Fig. 5.4 if the amplifier is to operate over a frequency range from 2 kHz to 10 kHz.

Date posted: August 15, 2019 . Answers (1)
What is the role of emitter bypass capacitor C_E in CE amplifier circuit shown in Fig. 5.3 ? Illustrate with a numerical example. (Solved)

What is the role of emitter bypass capacitor C_E in CE amplifier circuit shown in Fig. 5.3 ? Illustrate with a numerical example.

Date posted: August 15, 2019 . Answers (1)
Show and explain a Practical Circuit of Transistor Amplifier (Solved)

Show and explain a Practical Circuit of Transistor Amplifier

Date posted: August 15, 2019 . Answers (1)
Define Single Stage Transistor Amplifier and explain how it works (Solved)

Define Single Stage Transistor Amplifier and explain how it works

Date posted: August 15, 2019 . Answers (1)
For a single stage transistor amplifier, the collector load is R_C = 2 kilo-ohms and the input resistance R_i = 1 kilo-ohm. If the current... (Solved)

For a single stage transistor amplifier, the collector load is R_C = 2 kilo-ohms and the input resistance R_i = 1 kilo-ohm. If the current gain is 50, calculate the voltage gain of the amplifier.

Date posted: August 15, 2019 . Answers (1)
If the collector current changes from 2 mA to 3mA in a transistor when collector- emitter voltage is increased from 2V to 10V, what is... (Solved)

If the collector current changes from 2 mA to 3mA in a transistor when collector- emitter voltage is increased from 2V to 10V, what is the output resistance?

Date posted: August 15, 2019 . Answers (1)
A change of 200 mV in base-emitter voltage causes a change of 100 µA in the base current. Find the input resistance of the transistor. (Solved)

A change of 200 mV in base-emitter voltage causes a change of 100 μA in the base current. Find the input resistance of the transistor.

Date posted: August 15, 2019 . Answers (1)
What does the performance of a transistor amplifier depend upon? (Solved)

What does the performance of a transistor amplifier depend upon?

Date posted: August 15, 2019 . Answers (1)
What is the Output from Transistor Amplifier? (Solved)

What is the Output from Transistor Amplifier?

Date posted: August 15, 2019 . Answers (1)
Determine the Q point of the transistor circuit shown in Fig. 4.40. Also draw the d.c. load line. Given ß = 200 and V_BE =... (Solved)

Determine the Q point of the transistor circuit shown in Fig. 4.40. Also draw the d.c. load line. Given β = 200 and V_BE = 0.7V.

Date posted: August 15, 2019 . Answers (1)
In the circuit diagram shown in Fig. 4.39 (i), if V_CC = 12V and R_C = 6 kilo-ohms, draw the d.c. load line. (Solved)

In the circuit diagram shown in Fig. 4.39 (i), if V_CC = 12V and R_C = 6 kilo-ohms, draw the d.c. load line. What will be the Q point if zero signal base current is 20μA and β = 50?

Date posted: August 15, 2019 . Answers (1)
For the circuit shown in Fig. 4.38 (i), draw the d.c. load line. (Solved)

For the circuit shown in Fig. 4.38 (i), draw the d.c. load line.

Date posted: August 15, 2019 . Answers (1)