Yes, the whole idea is to have the transistor of the second
optoisolator running from a totally isolated supply. For
best results the two supplies should have the same value.

The two emitter resistors should be matched (equal) for best
results. The exact value you use is not that critical,
but I have found 1.5k to be a good choice.

Fr. Tom McGahee

-----Original Message-----
From: Gennette Bruce <bruce.gennette@TAFE.NSW.EDU.AU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Wednesday, March 08, 2000 7:10 PM
Subject: Re: [OT] 4N35 OPTO as analog isolator


>Here's a drawing in word format of what goes where -
> <<isolated follower.doc>>
>Red is +V
>Black is 0V
>orange is signal in/out
>blue is feed back paths
>
>Someone who knows - could the second isolator transistor have a completely
>separate supply, and would its resistor have to be proportionatly sized to
>match the voltage ratios?
>
>Bye.
>
>> ----------
>> From:         PDRUNEN@AOL.COM[SMTP:PDRUNEN@AOL.COM]
>> Reply To:     pic microcontroller discussion list
>> Sent:         Thursday, 9 March 2000 10:08
>> To:   PICLIST@MITVMA.MIT.EDU
>> Subject:      Re: [OT] 4N35 OPTO as analog isolator
>>
>> In a message dated 3/8/00 5:21:18 PM EST, tom_mcgahee@SIGMAIS.COM writes:
>>
>> << The output of an opamp is connected via a 47 ohm resistor to the Anode
>> of
>>  the first optoisolator LED. The cathode of the first optoisolator LED is
>>  connected
>>  in series to the Anode of the second optoisolator. The cathode of the
>> second
>>  optoisolator LED is connected to ground.
>>   >>
>>
>> Thanks Tom,
>>
>> But I failed to see where the analog input signal is applied.
>>
>> Paul
>>
>