AM modulator

Nov 05, 2004 5 Replies
E

Hi all,



Im trying ot build a very simple AM modulator with a small op-amp, bascially the carrier is fed into the amp input (as normal audio) then im using a transistor to alter the other input side in attempt to alter the volume, I can't however for the life of me get it to work.... I've also tried a resistor in the carrier line, then pulling the output side of the resistor down to ground with the modulation wave, this to me should work though no matter what I do it just dont seem to work at all :(



has anyone got any simple solutions to this ?



thanks


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D

--

I believe something is missing, and the OP may not work at the Carrier frequency.

What frequency is the carrier? What means are you using to multiply the two signals. What type Op Amp?

Don

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R

------------- Look up "Gilbert Cell" and VCA.

-Steve

-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!! http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
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E

thanks everyone, ive got some ideas of more things to try now,

chris

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J

bascially

This modulator circuit is very simple. As the gain control voltage is varied from 10V to 0.5V the gain drops from 100X to nothing. (Pretty much any small signal transistor will work).

Gain Control .-----o 0.5 to 10V | .-. | | 2k2| | '-' Audio In ___ | || (say 10mVpp) .-|___|------o---||----o Audio out | 470k | || 0 to 1Vpp || ___ | |/ 47uF o-||--|___|----o----------| || 1k BC546 |> o o 47uF | | | | | '---------------------------|---------' === GND

(created by AACircuit v1.28 beta 10/06/04

formatting link

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