Wien Bridge Oscillator

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Designing a simple oscillator circuit using the Wein Bridge

Transcript of Wien Bridge Oscillator

SINE WAVE GENERATIONUsing Wien Bridge Oscillator 741 Op amp

Sine Wave Generation

By Engr. Khurram Hashmi

Wien Bridge (Often used as AC Bridge)

Feedback and Gain

741 Open loop gain : 200,000 Gain with feedback Where is feedback factor Feedback may be Positive or Negative Wien Bridge oscillator utilizes positive voltage series feedback

Feedback Circuits

Oscillator Operation

When positive feedback is used in an amplifier with closed loop gain |Af| >1 ,the amplifier acts as an oscillator No input signal is required to set an oscillator circuit into oscillations. When A>1 the noise voltage present in the circuit is amplified The closer A to 1. The purer the sinusoid produced.

Oscillator Operation

Wien Bridge OscillatorVCC

-VEEOutput Sinusoid


Feed back

Design formulae

Output Signal frequency For simplification we take and Then Feedback resistors ratio

Design Calculations

Choosing output frequency and choosing We get

3300pF standard values were used R3=330 k and R4= 67 k such that

Designed circuit

Output Waveform

fo 1 kHz Amplitude 20 Vp-p