15.20 Design the Wien-bridge oscillator for operation at 10 kHz using R = 10 kΩ. If at 10 kHz the op amp provides an excess phase shift (lag) of 5.7°, what will be the frequency of oscillation? (Assume that the phase shift introduced by the op amp remains constant for frequencies around 10 kHz.) To restore operation to 10 kHz, what change must be made in the shunt resistor of the Wien bridge? Also, to what value must R2/R1 be changed?
C = 1.59 nF; 8.6 kHz; change the shunt resistor to 7.5 kΩ and R2/R1 to 2.35.