Hello there.
In the Texas Instruments application note AN-263, it describes a Wein Bridge oscillator that is enhanced by the addition of a FET. The diagram shows a 7.5V Zener diode in the circuit. Now, typical op-amp circuits presume a +/- 15 volt power supply, but I might have to use a +/- 12V Supply. It seems not unreasonable that this might affect the voltage that one would use for the zener. The scope traces on the page show the circuit using much of the 15V rails. Is there some reason that I might want to change the Zener diode voltage from what is shown?
In the Texas Instruments application note AN-263, it describes a Wein Bridge oscillator that is enhanced by the addition of a FET. The diagram shows a 7.5V Zener diode in the circuit. Now, typical op-amp circuits presume a +/- 15 volt power supply, but I might have to use a +/- 12V Supply. It seems not unreasonable that this might affect the voltage that one would use for the zener. The scope traces on the page show the circuit using much of the 15V rails. Is there some reason that I might want to change the Zener diode voltage from what is shown?
See Fig 4 in the obsolete data sheet. It is not too clear but helps with stability. Changing its value will have little affect. As the gate goes negative the JFet stops conducting, allowing the inverting input to set unity gain.
It controls the time constant and the diodes are reverse biased to ensure the oscillator gets a 'kick' to start it at the right point.
It controls the time constant and the diodes are reverse biased to ensure the oscillator gets a 'kick' to start it at the right point.
He's probably referring to the fact that the LF155 was introduced shortly after dirt was invented. That said, if you have the parts there's nothing wrong with building the circuit.
I wouldn't expect super high performance from that circuit but you should be able to get down around 0.1 % THD. Maybe better. It'll look like a sine wave on a scope. You can get some ideas for better circuits if you need better performance here: https://www.diyaudio.com/community/threads/low-distortion-audio-range-oscillator.205304/
Tom
I wouldn't expect super high performance from that circuit but you should be able to get down around 0.1 % THD. Maybe better. It'll look like a sine wave on a scope. You can get some ideas for better circuits if you need better performance here: https://www.diyaudio.com/community/threads/low-distortion-audio-range-oscillator.205304/
Tom