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Design >> Analog Design >> 1.5x voltage multiplication
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Message started by msudans on Oct 18^th, 2007, 7:21am

Title: 1.5x voltage multiplication
Post by msudans 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

Title: Re: 1.5x voltage multiplication
Post by ACWWong on 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

Title: Re: 1.5x voltage multiplication
Post by msudans on 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.

Title: Re: 1.5x voltage multiplication
Post by ACWWong on 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

Title: Re: 1.5x voltage multiplication
Post by RobG on 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

Title: Re: 1.5x voltage multiplication
Post by Aigneryu on 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