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TOPIC: running on 3.3 volts

running on 3.3 volts 11 months 3 weeks ago #1414

  • brownt
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HI,

I am using the opamp input stage at 3.3 volts. However, the output waveform is pulsating. What changes can I make to the opamp circuit so it will run ok at 3.3 volts. I am using MCP602 rather than a TL972.

Actually, it seems the opamp circuit is not the problem, but rather the inferior supply I am using for the arduino. I am using a pro Mini and the supply is through the jack of another device, and to prevent short circuiting there is a resistor in series which is causing havoc, I think.

thanks
Last Edit: 11 months 3 weeks ago by brownt.
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running on 3.3 volts 11 months 3 weeks ago #1415

  • Ray
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Checking the datasheets:
www.ti.com/lit/ds/symlink/tl972.pdf
www.mouser.com/ds/2/268/21733h-26779.pdf

Seems that both could work at 3.3V (although I never tried such a low power supply).
Which virtual ground are you using? (it should be 1.65V).
The standard Arduino UNO board works on 5V and the ADCs maximum span is 5V, so using an input analog signal of 3.3V will reduce the SN ratio.

The best way to debug it would be to use the sinewave generator to make sure that the output stage works fine.
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