problem with this schema

[mik]

I don't know why this mixed feedback topology doesn't works.

http://twin-x.com/groupdiy/displayimage.php?pos=-1268

I've checked all , but doesn't works..damn !

M.

 

[bcarso]

To begin with, assuming your input from the right is a.c. coupled (although no capacitor is shown), you appear to be driving the top winding with an op amp whose output is sitting at 24V d.c.! The current will be substantial with that 15 ohm resistor to ground.

 

[JohnRoberts]

Just to second what Brad is saying transformers do not tolerate DC well so both are going to be unhappy as drawn.

Positive feedback usually causes instability.

What are you trying to accomplish?

JR

 

[Samuel Groner]

Positive feedback usually causes instability. What are you trying to accomplish?

Negative output impedance (see feedbck.pdf). Should not cause instability here (without checking the schematic in detail, as the most important point has been mentioned allready).

Samuel

 

[mik]

I see , it's a DC problem.. the op Amp is really too hot...

As Samuel say, i'm tring to drive a trasformer with negative impedace..
now i've add a coupling caps, would you check the polarity please?

and "R14 bis" should be to ground or were I've put it, ( seems more logical )
If I've to ground it, were I have to link it ; up on R20 ?

my problem is to power the net with a single polarity PSU

thank you.

http://twin-x.com/groupdiy/displayimage.php?pos=-1269
M.