# Oscillators

Types of Oscillators
1. Tuned LC Oscillator :
where, L1 is the inductance in Henry
C1 is the capacitance is Farad
f is the output frequency in Hertz

Fig. : Tuned LC oscillator

1. Hartley Oscillator

where LT = L1 + L2 + 2M

The Hartley Oscillator consists of a parallel LC resonator tank circuit whose feedback is achieved by way of an inductive divider.

Fig. : Hartley oscillator

1. Colpitt’s Oscillator
The basic configuration of the Colpitts Oscillator resembles that of the Hartley Oscillator but the difference this time is that the centre tapping of the tank sub-circuit is now made at the junction of a “capacitive voltage divider” network instead of a tapped autotransformer type inductor as in the Hartley oscillator.
The frequency of oscillations for a Colpitts Oscillator is given as:

Fig. : Colpitt’s oscillator

1. Phase shift RC Oscillator :

where N is the number of RC stages (N = 3)

Fig. (d) : Phase shift RC oscillator

1. Crystal oscillator :

Series resonant frequency
Parallel Resonant Frequency
where

Fig. : Crystal oscillator

1. Wien Bridge Oscillator :

or R = R1 = R2; C = C1 = C2
=

Fig. : Wien bridge oscillator