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msudans New Member Offline Posts: 5 India	1.5x voltage multiplication Oct 18^th, 2007, 7:21am Can someone point me to a 1.5x voltage multiplication circuit, i.e, Vout=1.5*Vin ? Thanks
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ACWWong Community Fellow Offline Posts: 539 Oxford, UK	Re: 1.5x voltage multiplication Reply #1 - Oct 18^th, 2007, 7:55am a non-inverting op-amp structure is one way... with R2/R1 = 0.5 http://en.wikipedia.org/wiki/Operational_amplifier_applications
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msudans New Member Offline Posts: 5 India	Re: 1.5x voltage multiplication Reply #2 - Oct 19^th, 2007, 5:18am Hi, I did not word the question properly.. I'm looking for a 1.5x circuit in the context of charge pumps. Thanks for the reply anyway.
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ACWWong

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Oxford, UK

Re: 1.5x voltage multiplication
Reply #3 - Oct 19^th, 2007, 6:23am

I am assuming you want to increase a supply/reference voltage by 1.5 times using a charge-pump circuit so that it becomes outside the normal range of the supply (i.e. a voltage boost circuit) ?

If so, you can still use a non-inverting opamp structure to control the chargepump circuit.
The output of the opamp (working within the nominal supply voltage) can be controlling an oscillator which is used to drive a charge-pump circuit. The output of the chargepump circuit (i.e the boosted voltage) is fed back by the resistive divider in the non-inverting opamp loop, such that the chargepump output is maintained at (1+(R2/R1)*Vref.

Look up charge-pump circuits in a few textbooks, something like Baker's "CMOS Circuit Design, Layout and Simulation" would be a good start.

Cheers
aw

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RobG

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Bozeman, MT

Re: 1.5x voltage multiplication
Reply #4 - Oct 25^th, 2007, 8:26pm

msudans wrote on Oct 18^th, 2007, 7:21am:

Can someone point me to a 1.5x voltage multiplication circuit, i.e, Vout=1.5*Vin ?

Thanks

I think you are looking for something like...
1) charge two caps in series up to Vin.
2) put these two caps in parallel - this gives you Vin/2 (in steady state)
3) put these two caps in series with Vin - this gives you about 3/2*Vin minus whatever your load pulls off the caps.

This is very power efficient and doesn't depend on cap matching, but bottom plate parasitics will really mess things up so big external caps are normally used for this sort of thing.

rg

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Aigneryu Senior Member Offline Posts: 102	Re: 1.5x voltage multiplication Reply #5 - Nov 21^st, 2007, 10:26am Use parametric amplification of Cgs in MOS transistor, you can play with 1/2Cox WL to 2/3 CoxWL But this is 1.33x
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