Author Topic: NE555 as chargepump.... how does that work?  (Read 389 times)

cooder

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NE555 as chargepump.... how does that work?
« on: May 20, 2020, 03:22:55 AM »
Just looking at Vfe schematics to learn and understand stuff, Peter uses the NE555 chip which is dirt cheap as chargepump in some circuits.
This example is from the Fiery Red Horse. Can someone explain me how that works and what voltages can we coax out of that, what are advantages and downsides to the more usual TC1044 circuits? Thanks!

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tcpoint

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Freppo

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Re: NE555 as chargepump.... how does that work?
« Reply #2 on: May 20, 2020, 02:13:07 PM »
Dave Smith has a video that explains the theory behind the voltage doubler and inverter. :)


You can use almost any oscillator really (like the 555 example) together with a few diodes and capacitors.
But the current capability and voltage stability will be vastly inferior to a dedicated chargepump chip.

I designed a discrete (transistor based) voltage inverter to suit my manhattan style build (the Darby Fuzz).
Wrote about it here: https://www.parasitstudio.se/building-blog/manhattan-style-pedalbuilding
I forgot to draw a schematic for it, but you can probably reverse engineer from the layout if you are interested. :P
It has a bit of a voltage drop under load and can only supply a few mA, but works well for a germanium fuzzface.

The frequency isn't critical, but I tuned it to around 40khz to stay above the hearing range (nyquist frequency).

cooder

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Re: NE555 as chargepump.... how does that work?
« Reply #3 on: May 20, 2020, 02:54:02 PM »
Thanks for the swift reply, gentlemen!
More to wrap my head around later tonight...  ;)
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thesmokingman

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Re: NE555 as chargepump.... how does that work?
« Reply #4 on: May 20, 2020, 11:07:31 PM »
this is funny because I once asked Peter about this back when I got a v1 old school off of ebay that wasn't working ... he was kind enough to pass the knowledge along
once upon a time I was Tornado Alley FX