Which of the following statements about the Wien Bridge Oscillator is CORRECT?

Explanation:

Wein bridge oscillator is the commonly used circuit for generating a sinusoidal waveform of the required frequency.

Wein bridge oscillator:

The circuit diagram of the Wein bridge oscillator is shown below:

• The Wein bridge oscillator uses two RC networks connected together to produce a sinusoidal oscillator.
• The Wein bridge oscillator uses a feedback circuit consisting of a series RC circuit connected with a parallel RC of the same component values producing a phase delay or phase advance depending upon the circuit frequency
• At the resonant frequency, the phase shift is 00.

The feedback network consists of series and parallel connections of two RC networks that act as a lead-lag network in feedback.

Here Z_p and Z_s form a voltage divider and voltage across Zp will act as feedback voltage.

\(V_f=\frac{V_oZ_p}{Z_p+Z_s}\)

\(β=\frac{V_f}{V_o}=\frac{Z_p}{Z_p+Z_s}\)

On putting values of Z_p & Z_s, we will get the value of β as:

\(\beta=\frac{1}{3 \ + \ j(ω RC-\frac{1}{ω RC})}\)

Open-loop gain of the above circuit is:

\(A=1 \ + \ \frac{R_2}{R_1}\)

So loop gain will be:

\(Loop \ Gain=\frac{A}{3 \ + \ j(ω RC-\frac{1}{ω RC}) }\)

At ω = ω₀, the phase of loop gain must become zero and hence imaginary part should be zero.

\(\omega _o-\frac{1}{\omega_oRC}=0\)

\(\omega _0=\frac{1}{RC}\)

\(f _0=\frac{1}{2\pi RC}\)

Here f₀ is the frequency of oscillation.