Author Topic: Wein Bridge Curve Tracer Followup  (Read 325 times)

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Offline ZielsziekTopic starter

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Wein Bridge Curve Tracer Followup
« on: March 12, 2025, 06:43:07 pm »
A while ago I posted a problem I had with a curve tracer build. Now I have made some adjustments to the design and I was able to confirm that I was shipped some fake integrated circuits. The 150 Hz part is working fine but I cannot get the higher frequency part to oscillate. For some strange reason I am getting a 1 Hz sine wave. On a breadboard I was able to get the circuit to oscillate with 68 nF caps for the high frequency range. I tried using such capacitors here but to no avail.
I have tried fiddling around with the values for the resistors but I cannot make it work. I am sure I used the values in the schematic for the caps and resistors. Solder defects have been ruled out. I am aware that by design is not optimal but I do not require high stability for the frequencies. All I want is to have a high frequency range and a low frequency range.
Thank you for your time.

 

Offline Kleinstein

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Re: Wein Bridge Curve Tracer Followup
« Reply #1 on: March 12, 2025, 07:16:38 pm »
My guess would be on a mix up with the capacitors, like 10 µF instead of 10 nF.
Another possibilty could be the virtual ground oscillating: the LM358 may not be that happy with all the capacitve load (2 x 10 µF).
 

Offline ZielsziekTopic starter

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Re: Wein Bridge Curve Tracer Followup
« Reply #2 on: March 16, 2025, 02:24:30 pm »
Thank you very much for your answer. Indeed the virtual ground was oscillating. 1 nF fixed it right up. Sorry for the late answer and than you for your patience!
 


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