[sdiy] Multiplier built from op-amp

[harry]

Er... you could do it with diodes, or a bipolar transistor as well...
but I agree... the OTA would be the easiest / best way....

H^) harry

patchell wrote:

>     I assume you are refering to using the JFET as a voltage controlled
> resistor...
>
>     But, No, there is no way to make a multiplier out of a regular opamp...which
> is a shame when you think about it.
>
>     To make a multiplier you need something whose gain is dependent on some
> variable (current, voltage).  Your best bets are Operational Transconductance
> Amplifiers (OTA), such as the CA3080, CA3280, LM13600, LM13700, NE5517...and a
> few others I am sure.
>
>     You can also use discrete transistors or transistor arrays to do the job,
> but, this gets a little more involved.
>
>     For Info on using the CA3280 goto
> :http://www.oldcrows.net/~patchell/archives/archives.html
>
>     You will find lots of misc info that can be applied to any OTA.
>
> Timo Weggen wrote:
>
> > Hello,
> >
> > does anyone of you know a way to build a voltage multiplier (or call it vca)
> > using op-amps without a JFET?
> > TIA.
> >
> > Timo
>
> --
>  -Jim
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> * Visit:http://www.silcom.com/~patchell/
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