Roff
Well-Known Member
I was going to propose splitting the supply and creating an artificial or "virtual" ground (hence my question in post #28), but gave up when DamoRC said he was using a 5V wall wart, and also because he might have a 30mA LED.
Attached is a scheme that uses a simple DC-DC converter to create ≈-2.8V. I added a DPDT switch for simplified gain switching. This scheme still needs a voltage regulator, or a separate reference voltage, to keep the output stable. If the LM331 can be made ratiometric, then it might work without a regulator, but that would seem to me like a poor design.
The .asc file is not identical to the posted schematic. I was mainly testing the interaction between the converter and the amplifier.
Attached is a scheme that uses a simple DC-DC converter to create ≈-2.8V. I added a DPDT switch for simplified gain switching. This scheme still needs a voltage regulator, or a separate reference voltage, to keep the output stable. If the LM331 can be made ratiometric, then it might work without a regulator, but that would seem to me like a poor design.
The .asc file is not identical to the posted schematic. I was mainly testing the interaction between the converter and the amplifier.
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