Yes when I first did this opamp tx circuit a couple of years ago,
I had the experience that decoupling the transformer solved VG
imbalance. I didn't need to refer it to actual ground IIRC.
In this case, initially that didn't work or wasn't enough.
However when I get time I will try it again on this one.
Once the TX is decoupled, what difference do you think it makes
referring it to actual ground rather than VG?
One would imagine the AC on the TX would average to 0v. I guess
if that's not the case there might be an issue.
It's a nuisance with my pcbs though I'll have to cut traces and
so on. Next revision I will leave the PCB agnostic as to TX
connections.
On 02/05/2025 23:19, Arjay1949 wrote:
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As to your other problem, I've personally found that AC
coupling the transformer to real ground, and including a series
resistor in the op-amp output seems to help with any strange DC
offset problems
Where I have had trouble in the past coupling an op-amp
output to a transformer, it's always seems to have been DC
coupling using the 'half rail' (Vgnd) as a reference that gives
stability? problems.
My simple OPIC circuit ( ) uses a 47uF cap to AC couple the
transformer output, which is then refernced to ground, rather
than ''half rail'.?
I've had no DC offset problems at all that I can detect or
measure..?
