I would like to design a circuit with an AOP which will have a variable gain controlled by a tension (a ramp). Could you help me and explain me the circuit please?
Thank you,
Farad
3
-
1\$\begingroup\$ It is called a multiplier. It is also called a Variable Gain Amplifier (VGA). Go forth and Google. \$\endgroup\$– WhatRoughBeastCommented Jan 20, 2016 at 17:54
-
\$\begingroup\$ This is unrelated to this question but, Dave Tweed and I answered this question a while back - did you not understand the answers: electronics.stackexchange.com/questions/209607/… \$\endgroup\$– Andy akaCommented Jan 20, 2016 at 18:20
-
\$\begingroup\$ WhatRoughBeast as you see on the title I know it is a VGA... Google show me some circuit but It don't do what I want... Thank you Andy, I forgot to answer.. I will! \$\endgroup\$– uFaradCommented Jan 21, 2016 at 9:24
Add a comment
|
1 Answer
\$\begingroup\$
\$\endgroup\$
1
For those who are interrested by the answer. I used a multiplier as a VGA. In order to create this function I used :
- 2x Log amplifier
- 1x sum amplifier
- 1x Exp amplifier
If I want multiply a signal V1 with a signal V2 =>
exp(log(V1)+log(V2)) = V1 * V2
The following figure is the result :
-
\$\begingroup\$ Please note that that will only work as a first-quadrant amplifier. That is, both inputs must be positive, so showing V1 as an AC signal is misleading. Second, it's not a very good amplifier, without much bandwidth or dynamic range. It may be good enough for your (unstated) purpose, but it may not. \$\endgroup\$ Commented Mar 24, 2016 at 19:53