Operational amplifier circuits for the Wien-bridge oscillator

As the frequency of operation increases, the poles of the Wien-bridge oscillator depart from the imaginary axis because of the frequency dependence of the amplifier gain. By properly shaping the magnitude and phase response of the amplifier, it is possible to keep the poles on the imaginary axis at much higher frequencies than is normally expected, thus extending the range of operation of the oscillator. Experimental results verify the vast improvement that is predicted.