Unable to get a Wien bridge oscillator to work

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Discussion Overview

The discussion centers around troubleshooting a Wien bridge oscillator circuit that a participant has built but is experiencing inconsistent functionality. The conversation involves exploring the circuit design, component values, and operational amplifier connections, with a focus on understanding why the circuit sometimes works and sometimes does not.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant reports intermittent success with their Wien bridge oscillator circuit, noting that it sometimes causes a LED to blink.
  • Another participant asserts that the drawn circuit does not represent a true Wien bridge oscillator and suggests it may function as a digital oscillator instead.
  • Several participants request additional details about the circuit, including component values and the type of operational amplifier used.
  • Concerns are raised about the placement of components and the necessity of a proper power supply connection for the op-amp.
  • There are discussions about the critical gain settings required for oscillation and the potential need for an amplitude limiter.
  • One participant mentions the importance of grounding and the relationship between the op-amp output and the power supply voltage.
  • Another participant provides a reference to a proven Wien bridge oscillator schematic and suggests using a dual power supply for better performance.
  • There is a suggestion that the circuit may not be suitable for simply blinking an LED due to its design purpose.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the circuit design, with some asserting it is not a proper Wien bridge oscillator while others defend their approach. There is no consensus on the specific reasons for the circuit's failure to operate consistently, and multiple competing views on troubleshooting methods remain.

Contextual Notes

Participants highlight the importance of providing complete circuit schematics and component values for effective troubleshooting. There are unresolved questions regarding the power supply connections and the implications of using a single supply with the op-amp.

Who May Find This Useful

Individuals interested in circuit design, particularly those working with oscillators and operational amplifiers, may find this discussion relevant.

  • #31
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  • #32
@Svein
I agree. The gate voltage control circuit of a FET can have a longer time constant than a filament globe, and that does reduce harmonic distortion at low frequencies.
 
  • #33
Baluncore said:
@Svein
I agree. The gate voltage control circuit of a FET can have a longer time constant than a filament globe, and that does reduce harmonic distortion at low frequencies.
Here's another FET-stabilized Wien bridge oscillator I designed for a pitch theremin, which is an electronic musical instrument:

https://www.theremin.us/Circuit_Library/wienbridge.htm

And here's another circuit I designed using two Wien bridge oscillators (to make a pitch theremin). In this circuit, operational transconductance amplifiers are the regulating elements:

file:///C:/Users/Arthur/Desktop/Theremins/203%20Theremin/203.html

I particularly like the second circuit, however, the operational transconductance amplifiers are generally only available as residual stock, and therefore not recommended for new designs.
 
  • #34
Art Harrison said:
And here's another circuit I designed using two Wien bridge oscillators
That link is to your C: hard drive.
 

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