The circuit's DC operating point is simply 0V (it has a dual supply) by the 0V reference for the 1st opamp through R1, like all opamp linear circuits. I had one that bounced for minutes when its output frequency was 10Hz. It too had amplitude bounce because a lighbulb is slow to react. If the output amplitude increased, the lightbulb would get more power and its resistance would increase, which also increased the negative feedback resulting in reduced gain and the amplitude would be decreased back down to normal. Once started, the converter will converge rapidly over a few cycles of operation to a steady state where the reset step V p )C 2 /C 1 equals the ramp amplitude: T s (V cm V 1 )/R 1 C 1. Text: at the 4 stages, consisting of a square wave output, a triangle wave output, a sine wave output and. Years ago, Wien Bridge Oscillators used a simple lightbulb for amplitude control (Hewlett-Packard's very 1st product was a Wien Bridge Oscillator with a lightbulb).
Since the rectifier's output is filtered, it is delayed and the circuit's output amplitude takes time to settle. The circuit oscillates with a stable frequency that is at the maximum output frequency of the bandpass filter.Ī problem with Wien Bridge Oscillators is output amplitude bounce when the frequency is changed, and when they are first turned-on. The 2nd opamp is simply a filtered full-wave rectifier and its output controls the resistance of the FET for amplitude control. The 1st opamp's negative feedback resistors of R3, R4 and the FET give it a gain of 3 to make-up for the loss in the Wien Bridge network.
Reg:square wave to sine wave converter Hi, I am working with a feedback circuit for a sensor. The circuit that you posted is a common Wien Bridge Oscillator, that produces a sine-wave by using positive feedback around the 1st opamp by the bandpass-filter of the equal RC networks (the Wien Bridge). Square To Triangle Wave Converter Circuit.
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