I want to know about the working,principal of transistor as oscillator.

Asked by  | 25th Feb, 2012, 03:25: PM

Expert Answer:

An oscillator must have the following three elements

  • Oscillatory circuit or element.
  • Amplifier.
  • Feedback network.

The oscillatory circuit or element, also called the tank circuit, consists of an inductive coil of inductance L connected in parallel with a capacitor of capacitance C. The frequency of oscillation in the circuit depends upon the values of L and C. The actual frequency of oscillation is the resonant or natural frequency and is given by the expression

f = 1 / 2??LC Hz , where L is inductance of coil in henrys, and C is the capacitance of capacitor in farads.

The electronic amplifier receives dc power from the battery or dc power supply and converts it into ac power for supply to the tank circuit. The oscillations occurring in the tank circuit are applied to the input of the electronic amplifier. Because of the amplifying properties of the amplifier, we get increased output of these oscillations. This amplified output of oscilla­tions is because of dc power supplied from the exter­nal source (a battery or power supply). The output of the amplifier can be supplied to the tank circuit to meet the losses.

The feedback network supplies a part of output power to the tank or oscillatory circuit in correct phase to aid the oscillations. In other words the feedback circuit provides positive feedback.

Types of Transistor Oscillators:

A transistor can be operated as an oscillator for producing continuous undamped oscillations of any desired frequency if tank (or oscillatory) and feedback circuits are property connected to it. All oscillators under different names have similar function i.e. they generate continuous undamped output

Answered by  | 25th Feb, 2012, 04:22: PM

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