In the phase-shift oscillator in Figure 15.15, the capacitor at the noninverting terminal of op-amp \(A_{1}\) is replaced by a variable capacitor \(C_{V}\).

(a) Derive the expression for the frequency of oscillation.

(b) If \(C=10 \mathrm{pF}, R=10 \mathrm{k} \Omega\), and \(C_{V}\) is variable between 10 and \(50 \mathrm{pF}\), determine the range of oscillation frequency.

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C v (v) o HH ww R ww R A2 102 V3 A3 + + A1 V2 + www R Figure 15.15 Phase-shift oscillator circuit with voltage-follower buffer stages