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Negative voltage for a project
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Saitama:
Hello! I am designing a Lab bench power supply with OpAmps and i ran into a problem.
The problem is that i need negative voltage for a differential amplifier, so naturally, I searched for a 7660, but could not find any in my region and buying from Ebay will take an eternity so I came here to ask.
My input voltage is 32V and the Amp need -2V. I am looking for a circuit that is cheap and stable.
Any suggestion is welcome.
Thanks in advance!
Benta:
If it's an AC powered bench supply, you can make a small charge pump from the secondary with two diodes and two caps.
Saitama:
I already have a 32V unadjustable power supply, so i can't do that.
xavier60:
A CMOS 555 could drive the charge pump. The CMOS 555 will oscillate properly simply with a resistor from its output to pins 2 and 6 tied together, and a capacitor from pins 2 and 6 to GND.
It can be powered with a dropper resistor and bypass capacitor with a shunt regulator across the -DC output.
Audioguru:
I assume that your power supply will use AC electricity and a transformer. Then here is how a low negative voltage is made in another power supply circuit:
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