Author Topic: Negative voltage for a project  (Read 842 times)

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Offline SaitamaTopic starter

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Negative voltage for a project
« on: July 04, 2019, 05:56:00 pm »
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!
 

Offline Benta

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Re: Negative voltage for a project
« Reply #1 on: July 04, 2019, 06:14:23 pm »
If it's an AC powered bench supply, you can make a small charge pump from the secondary with two diodes and two caps.
 

Offline SaitamaTopic starter

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Re: Negative voltage for a project
« Reply #2 on: July 04, 2019, 07:34:20 pm »
I already have a 32V unadjustable power supply, so i can't do that.
 

Offline xavier60

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Re: Negative voltage for a project
« Reply #3 on: July 04, 2019, 09:30:44 pm »
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.
HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 

Offline Audioguru

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Re: Negative voltage for a project
« Reply #4 on: July 05, 2019, 02:22:33 am »
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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