Wien bridge oscillator - with high stability

with high stability The Wien bridge oscillator is a com- monly used circuit, which is not sur- prising considering that it has low distortion and its resonant frequency can quite easily be made adjustable. This resonant frequency depends on a pair of resistors (each = R) and a pair of capacitors (each = C) and is defined by the formula f = 1/2nRC. In the circuit shown here R consists of R1 + P1a (or R2 + P1b) and C is either C1, C2 or C3 (or, C4, C5 or C6). The oscillator proper consists of these components together with IC1, IC2 and their associated com- ponents. Part of the output signal from IC2 is fed to the regulating attenuator con- sisting of IC3 and T1. This FET, which is used here as a variable resistor, is part of the feedback loop of IC2. The gain of this op-amp is thus made voltage dependent and can be changed by altering the control voltage of T1 using P2. This potentiometer must be set so that the circuit oscillates stably. The range of the oscillator, with the com- ...