# RF Wireless World

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## Oscillator types-wein bridge,colpitts,clapps,hartley,crystal oscillator

The page covers oscillator types viz. wein bridge oscillator,colpitts oscillator,clapps oscillator,Hartley Oscillator and crystal oscillator. They are used in many electronic circuits as reference oscillator in PLL/synthesizer circuits.

### wein bridge oscillator

The figure depicts circuit of wein bridge oscillator using operational amplifier. As shown frequency of oscillation depends on following equation.
f = 1/2*π*(R3*R4*C1*C2)0.5
Where,
If R3=R4=R and C1=C2=C then equation reduced to
f = 1/2*π*R*C

### colpitts oscillator

The figure depicts circuit of colpitts oscillator using transistor. As shown frequency of oscillation depends on following equation.
f = 1/2*π* ( L *(C1*C2/C1+C2) )0.5
gm*Rc >= C2/C1

### Hartley Oscillator

In the figure-2(colpitts oscillator) above if we replace C1,C2 with L2,L2 and C in place of L then it will become Hartley Oscillator. Frequency of oscillation for Hartley Oscillator is as per following equation.
f = 1/2*π*(C(L1+L2))0.5
gm * RC >= L1/L2

### clapps oscillator

In the colpitts oscillator circuit if inductor is replaced by a variable capacitor(say, C3) then frequency of oscillation is expressed as per following equation. The circuit will become clapps oscillator.
f = 1/2*π*(L*C3)0.5
It happens if (C1/C >> 1 ) and (C1/C)>>(C1/C2)

### crystal oscillator

The figure depicts circuit of crystal oscillator. The series resonance frequency is expressed as,
fs = 1/ 2*π*(L*C)0.5
The parallel resonance frequency is expressed as,
fp = 1/2*π*(L*Ceq)0.5 ,
Where,
Ceq = C*Co/(C+Co)

The frequency of oscillation is chosen between fs and fp. For more refer Quartz Crystal page.