jgk@osc.COM (Joe Keane) (09/01/90)
I'm interested in building a bunch of voltage-controlled amplifiers, and i'd like to know what are the best ways of doing this. My requirements are that it have low noise, high linearity with respect to the input voltage, and reasonable linearity with respect to the control voltage. The techniques i've seen include: FETs as variable resistances; four-quadrant multiplier ICs; opto-isolators as variable resistances; OTAs (operational transconductance amplifiers); balanced modulators using non-linear devices; and probably some more i can't think of right now. I'd like to know if any of you have an opinion about the pros and cons of these or other techniques, or know how this is usually done in stereo equipment or analog synthesizers. E-mail to me and i'll summarize, and thanks in advance for your help.