Test: Colpitts Oscillator - Electronics and Communication Engineering (ECE) MCQ

Voltage series feedback is used in Colpitts oscillator. In voltage series feedback a part of output voltage is fed back to input.

Capacitor with a center tap is used in feedback system of Colpitts oscillator.

In a Colpitts oscillator, capacitors are primarily used in the feedback system. The Colpitts oscillator typically consists of two capacitors and one inductor. One of the capacitors forms a voltage divider with other circuit elements, providing the necessary feedback for oscillation. So, option 3: Capacitor is the correct answer.

Capacitive voltage divider network is used for giving positive feedback in Colpitts oscillator.

There are two capacitors in the tank circuit of Colpitts oscillator and it is given for voltage division.

There are one inductor in the tank circuit of Colpitts oscillator and it is given for oscillation.

Capacitive circuit in the colpitts oscillator improves frequency stability of oscillator.

The active element used in Colpitts oscillator is transistor and it is used for amplification of weak oscillator signals.

RFC choke present in Colpitts oscillator is to provide high reactance to AC oscillation and low reactance to DC supply to improve performance.

RFC choke present in Colpitts oscillator is to provide high reactance to AC oscillation and low reactance to DC supply to improve performance. If resistor is used there will be some power loss in DC biasing which is unnecessary.

Resistors are provided in Colpitts oscillator to bias transistor to its DC operating point.

 The frequency of colpitts oscillator is expressed as 1/(2ᴨ√LC) where L is inductance and C is effective capacitance.

Colpitts oscillator as normal oscillator uses positive feedback for oscillation to satisfy Barkhausen’s criteria.

 To ensure constant feedback gang tuning is used in Colpitts oscillator.

 In the tank circuit of Colpitts oscillator there are two capacitors connected in series and hence effective capacitance is (C1×C2)/(C1+C2).

Common emitter configuration is used for amplifying distorted oscillatory signal to a perfect oscillation.

The overall phase shift provided by tank circuit is 180 degrees. Since active element produces a phase shift of 180 degrees the tank circuit should create 180 degrees to obey Barkhausen’s criteria.

The gain device in Colpitts oscillator act as a band pass filter and thus limits frequency of oscillation to a certain range.

Amplitude of oscillation in Colpitts oscillator using describing function method is egual to
V=(2I_C R_L C2)/C1.

 Colpitts oscillator shows better frequency stability in high frequencies than Hartley oscillator.

Colpitts oscillator provide more performance than Hartley oscillator because of its capacitive feedback elements.