H11F1 opto for compressor?

[Aharon]

Anybody ever tried one of these for a compressor?.
IS it usable?.
Thanks
Aharon

http://www.fairchildsemi.com/ds/H1/H11F1.pdf

 

[PRR]

> IS it usable?.


Maybe.

Note that to stay in the linear resistance range, the peak signal level has to stay below 100mV at high resistances, as low as 10mV for low resistances.

In the standard compressor, your lowest resistance happens at the highest input levels.

So the voltage across the opto-FET has to stay around 5mV to 10mV maximum, followed by an amplifier with gain of 100 or 200 to get back to line level.

The maximum signal to noise ratio is around 72dB. Even if you use a low-noise amplifier, the series resistor is around 10K-100K and its noise will dominate when not limiting.

While the isolated control input offers some advantages, conventional audio FET limiters work fine with the FET common to audio and control voltages.

 

[Aharon]

Thanks PPR,there goes that idea......
Take care
Aharon

 

[clintrubber]

And how about using them for analog switching ?

I have ordered a few of these to toy around with. I'm building a simple electronically controlled source selection, a simple arrangement
with an inverting opamp and two input resistors with two series switches (doing an SPDT) to the virtual earth. And suitable AC-coupling, biasing etc.

For those switches I'll be either using JFETs (J112, with ramped control voltages) or those H11F1-devices. The topology can be a lot simpler with the latter method as it seems.

So I was wondering if anyone has already some experience with the H11F1/2/3.

I'm mainly concerned with switching-clicks - maybe I need to drive those H11F1 with some 10ms ramps as well.


Thanks,

Peter