In an OPAMP Wien Bridge Oscillator, two pairs of R and C are used
| In an OPAMP Wien Bridge Oscillator, two pairs of R and C are used when the frequency of oscillation is 200 kHz. If the value of C is 10 pF, find the value of R.
A. 59.98 kΩ
B. 79.58 kΩ
C. 88.67 kΩ
D. 68.87 kΩ
Please scroll down to see the correct answer and solution guide.
Right Answer is: B
SOLUTION
Concept:
The circuit diagram of Wein bridge oscillator is shown below:
The phase angle criterion for oscillation is that the total phase shift around the circuit must be 0°.
The total phase shift around circuit 0° occurs when the bridge gets balanced, which is at resonance.
∴ The frequency of oscillation is given by:
\({\omega _o} = \frac{1}{{RC}}\)
\({f_o} = \frac{{1}}{{2\pi RC}}\)
Calculation:
Given f0 = 200 kHz and C = 10 pF.
We can write:
\(200k = \frac{{1}}{{2\pi R(10\times10^{-12})}}\)
\(R = \frac{{1}}{{2\pi \times 200k(10\times10^{-12})}}\)
R = 79577 Ω
R = 79.58 kΩ
