Fairchild H11F1 Optocoupler - sound samples added

doctorvague · Last edited by doctorvague on Fri May 11, 2007 9:27 am; edited 1 time in total

Ran across this today:
http://www.fairchildsemi.com/ds/H1/H11F1.pdf
It appears this would work more or less, in place of a vactrol, yes-no?
With a turn-on time of 25uS. Hmmm. Not that I don't love the lazy 'thwip' of a vactrol...

Unless someone talks me out of it I'm ordering some of these and some Silonex "Vactrols" this week to blow u...I mean experiment with as alternatives to the VTL5C's.
Your thoughts?

Phil

We have knobs so we must twist them.

sohcahtoa · Joined: Aug 12, 2006 Posts: 55 Location: Fargo, ND

vactrol if I am not mistaken vary resistance, this is a circuit varies a transistor.

but after looking at the data sheet

As a remote variable resistor
•≤ 100 Ω to ≥ 300 M Ω with ≥ 99.9%
linearity which is exactly what you want.

Edit:
As a remote variable resistor
•greater than 100 ohms to less than 300 M ohms with greater than 99.9%
linearity which is exactly what you want.

funny I can write the ohm symbol in the editor but it does not post to the forum

bugbrand · Posted: Wed Apr 25, 2007 2:55 am Post subject:

Colin who does Experimentalists Anonymous always recommended then to me but I never got around to checking them... He's got good words, so they may well be very useful - do let us all know how your tests turn out!

Mikmo · Posted: Wed Apr 25, 2007 12:57 pm Post subject:

what would the advantage be ?

Price or performance or availability ?

doctorvague · Posted: Wed Apr 25, 2007 2:16 pm Post subject:

Thanks for the replies. I'm ordering some today and will report. They are somewhat more expensive than Vactrols, but they are way faster and appear to have a more linear curve, but we'll see how they do musically, etc. I'm a 'hook it up and see what happens' kind of DIY guy so if you want the algebra someone else will have to buy a couple and chime in. The example circuits are dead simple so that's a good sign Smile

clippin' alligators
Phil

doctorvague · Posted: Thu May 10, 2007 2:56 pm Post subject:

Hi all
My observations are that the H11F1 is largely interchangeable with the VTL's but as you would expect the transfer curve is different, which can be compensated for of course.
I've got a filter design which is nearly completed and have decided to use 3 different "vactrols" i.e. optocouplers including the H11F1, actually one of the the other opto's switches out with the H11F1 using a DPDT. In this filter design this chip has a buzzy quality and breaks up in a way that is very pleasing to my ear. If used moderately it can be pretty breathy- or actually 'woodwindy'.

This example uses 1 triangle wave and 1 square wave into the filter in 'buzz mode' (using the H11F1). It will overdrive more than this with more input, but this shows off some subtleties. Recorded dry, no VCA, straight into the mixer. Because of the magic of vactrols in many patches you don't need a VCA with this filter. The filter has a really short signal path and a pretty strange passive resonance circuit but doesn't resonate into oscillation. More later.

http://idisk.mac.com/doctorvague/Public/Clips/RF-1buzz1tri1square.mp3

Clippin' alligators,
Phil

doctorvague · Posted: Fri May 11, 2007 9:36 am Post subject:

Here's another sample using 2 H11F1's in an earlier version of the same filter as last post

http://idisk.mac.com/doctorvague/Public/Clips/Rubber1DwithH11F1chips.mp3

This one switches optos in the middle of the clip from the H11F1 to the NSL-32SR3. The other opto is a VTL5C2

http://idisk.mac.com/doctorvague/Public/Clips/RF-1_2sawbothmodes.mp3

these are straight to the board dry, not even using a VCA

Scott Stites · Posted: Fri May 11, 2007 10:47 am Post subject:

Herr Doktor -

I really like these samples. The woodwind sounding one is particularly interesting.

I was also able to hear some of the other jam files you turned me onto (am listening now). Simply marvelous! - have you posted anything like that in the music section here yet (I don't get there as much as I should)?

Cheers,
Scott

doctorvague · Posted: Mon May 14, 2007 6:06 am Post subject:

Just a second, Scott.... sorry I thought I heard a pin drop in the balcony. Wink

mediatechnology · Posted: Sat May 19, 2007 7:12 pm Post subject:

I've used the H11F1 in a few experiments and it's a very interesting part. Compared to a JFET it has the unique property of not having control feed-through. In a shunt configuration as a voltage-controlled-resistor it's limited to 50-100 mV or so due to distortion.

I did some nose gate experiments and it was very, very fast and makes a great switch.

doctorvague · Posted: Sun May 20, 2007 4:07 am Post subject:

mediatechnology · Posted: Sun May 20, 2007 8:26 am Post subject:

For control linearization, constant-current LED drive might be worth trying.

Another idea I had was to use the LED as a diode in a peak detector. The FET would then respond to charging current above the value stored on the hold capacitor. I don't know what practical use that might have, perhaps a means of detecting crest-factor, but it's fun to think about and maybe try in a peak-limiting application.

As the datasheet points out, used as a sample and hold it will have low charge injection. In an industrial application having the S/H control galvanically isolated is very useful.

Just thought of another one: Use the FETs as switches to form precision rectifiers. Use a single op amp polarity flipper with a single FET switching polarity. Drive the LED from a comparator-based zero crossing detector. Hmm...Think I want to try that one.

Modulator applications?

I've always thought that this simple part (the H11F1) has some amazing possibilities.

Has anyone done a multi-pole phaser with it?

Noiseconformist · Joined: Aug 05, 2008 Posts: 27 Location: Vienna

datasheet link has been changed to: http://www.fairchildsemi.com/pf/H1/H11F1M.html

mono-poly · Posted: Wed Aug 06, 2008 4:16 am Post subject:

This sounds pretty nice (ok late reply)

mediatechnology · Posted: Wed Aug 06, 2008 4:23 am Post subject:

Thanks for the new link to the H11F datasheet.

I had read (Digi-Key IIRC) that this part was going end-of-life and had last time buy status. The new datasheet, dated 2007, doesn't mention this and I hope that it has been kept in the Fairchild line. It's starting to look that way.

Noiseconformist · Joined: Aug 05, 2008 Posts: 27 Location: Vienna

you're welcome! (at least reason enough to end my lurking existence Wink

)

Noiseconformist · Joined: Aug 05, 2008 Posts: 27 Location: Vienna

mediatechnology · Posted: Wed Aug 06, 2008 3:56 pm Post subject:

I haven't used them in any filter topologies yet. That interests me particularly multi-pole phasers.

I tried them in a gate application, signal selector and voltage-controlled shunt attenuator.

As mentioned earlier by another poster the signal level (I tried it in shunt as a VCR) is limited to a pretty low level around 50 - 100 mV. THD rises rapidly after that.

The signal selector and gate used them in the virtual ground node of an op amp so the p-p voltage wasn't an issue.

doctorvague · Posted: Thu Aug 07, 2008 4:31 pm Post subject:

mediatechnology · Posted: Thu Aug 07, 2008 5:38 pm Post subject:

doctorvague · Posted: Fri Aug 08, 2008 4:39 am Post subject:

mediatechnology · Posted: Fri Aug 08, 2008 6:10 am Post subject:

The short answer to your question is: "it will just distort."

With regard to damaging the H11FM here's the long answer:

The FET continuous current absolute maximum is +/-100 mA. The LED continuous forward current absolute maximum is 60 mA.

>+/-100mA signal (FET) current or >60mA LED current would harm the device. It's doubtful that in most effects applications you could get that kind of signal current to develop during severe overdrive for the FET. In most applications the LED will be resistively current limited far below 60 mA.

In severe FET overdrive, at least in a shunt or variable R topology, the main thing you'll get is distortion - at least in carefully-designed circuits.

doctorvague · Posted: Fri Aug 08, 2008 6:26 am Post subject:

intellijel · Joined: Sep 10, 2006 Posts: 67 Location: Vancouver, BC

I am trying to drive the led of an H11F1M opto isolator .

The problem is that it seems to only have a range of 60-400 ohms and then suddenly jumps to infinite resitance. The data sheet seems to be missing very important information yet it claims a linear response over a huge range (without graphs to back this up mind you).

I have tried driving the led with transistor circuits and as part of the feedback path in an opamp.

I see some people here have used these succefully. Do you guys have any tips? Any schematics to share?

Ideally I would like to get a resistance in the range of 60ohms to 50k

Grumble · Posted: Mon Feb 22, 2016 5:21 am Post subject:

I know

this is an old thread...
I'm simmering about building a VCA and have been F.. playing around with the infamous LM13700, but could't get it to work the way I want.
Than I remembered about an opto FET I have been using some years ago, to use as a variable resistor in a potentiometer diagram.
Searching the NET I came across this (old, but not forgotten) thread and I think I have found the solution regarding the linearity of this VCA build.
You just need 2 H11F1's where 1 is on the feedback side and the other on the control side. (see attachment).
I think the bleeding of the control voltage to the output will be zero...
So I have ordered some of these opto FETs....

Source: EDN.com

fet_optocoupler potmeter.jpg

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