OSCILLATOR

It is a electronic circuit which produces oscillations. Essential requirements of an oscillator  A resonant circuit or a crystal which decides oscillatory frequency of an oscillator circuit is called tank circuit. Damped oscillations  Oscillations whose amplitude goes on reducing continuously are called damped oscillations. This type of oscillations are produced by sparking.

Types of Oscillator Circuits

 Ticker feedback, oscillator oscillator

 1.Hartley series fed and Hartley parallel fed oscillator

2.Colpitts :     It is an oscillator, which employs a crystal in place of LC lank circuit. It is renowned as a stable frequency oscillator. Employs capacitive feedback oscillator

•  Tuned Plate Tuned Grid (TPTG) oscillator
•  Electron coupled oscillator
•  Master oscillator power amplifier (MOPA) oscillator
•  Crystal oscillator
•  Multivibrator oscillator
•  Wein bridge oscillator
•  Neon lamp oscillator
•  Thyratron sweep oscillator
•  Phase shift RC oscillator
•  Beat frequency (BFO) oscillator
•  Klystron oscillator
•  Magnetron oscillator.

Classification of Amplifiers

1. Class ‘A’ amplifier : The amplifier circuit in which control-grid/base bias and signal voltages are adjusted in such a way that current in the output circuit flows for the entire duration of the input signal. This type of circuit has best fidelity, minimum distortion but low output power.
2. ‘B’ amplifier : It is the amplifier circuit in which control-grid/base sias and signal voltages are adjusted in such a way that current in the output circuit flows for less than half time of the input signal. This type of circuit has, minimum fidelity, maximum distortion but maximum output power .  These are used in push-pull audio stages . 
3. Class ‘AB’ amplifier : It is the amplifier circuit in which control-grid/base bias and signal voltages are adjusted in such a way that current in the output circuit flows for less than full but more than half time of the input signal.This type of circuits are utilized in ordinary type of equipments. Their efficiency is 35-50%. :
4. Class ‘C’ amplifier : It is the amplifier in which control-grid/base bias and signal voltages are adjusted in such a way that current in the output circuit remains for less than half time of the input signal. This type of circuit has, minimum fidelity, maximum distortion but maximum output power too. These are used for RF amplification in transmitters.