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High frequency noise

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Fish

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Hello,

What are possible causes of 50 kHz noise in a circuit? I built a simple inverting amplifier today using an LF356 opamp, but I persistently get a 50 kHz noise from the output on my oscilloscope. No amount of filtering seems able to get rid of it. Even when I remove call the capacitors from my circuits, leaving only non-reactive elements, this noise persists. It is something to due with my scope? Am I missing something? It's extremely irritating.
 
Fish said:
Hello,

What are possible causes of 50 kHz noise in a circuit? I built a simple inverting amplifier today using an LF356 opamp, but I persistently get a 50 kHz noise from the output on my oscilloscope. No amount of filtering seems able to get rid of it. Even when I remove call the capacitors from my circuits, leaving only non-reactive elements, this noise persists. It is something to due with my scope? Am I missing something? It's extremely irritating.

It sounds like your circuit is unstable, removing capacitors will only make it worse! - you may need to add a capacitor, to limit high frequency response, to make it stable.
 
Hi Fish,
The cable capacitance to my 'scope makes opamp circuits oscillate. If I connect the output of an opamp directly to a shielded audio cable the same.
Isolate the opamp from the cable capacitance with a series 100 ohm resistor, like shown on the opamps' datasheets.
 
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