Googled Z21806. Wow this is a zero field circuit with built in matched resistor. A trafo like this is what I wanted.
So, what is your problem? "Phase reversal" means ugly clipping behavior or absolute phase reversal? Why do you think phase margin failed? This circuit is basically inverting amplifier therefore such ugly clipping will not likely occur, I think, even it have some PFB.
So, what is your problem? "Phase reversal" means ugly clipping behavior or absolute phase reversal? Why do you think phase margin failed? This circuit is basically inverting amplifier therefore such ugly clipping will not likely occur, I think, even it have some PFB.
Hello,
The problem is that this "built in matched resistor" (i don't really know what do you mean) transformer gives me headache because one of the secondary seems to have a problem.
The central pin to others coil pin of the secondary is effectively returning a opposite phase signal the entire coil don't return anything.
Hello,
The xformer out of the circuit :
I put a 100mVpp 100Hz sinewave between 2 and 4
between 6 and 7 there is 100mV
between 8 and 9 there is 50mV
between 9 and 10 there is 50mV
between 8 and 10 there is 0mV
The xformer in the circuit :
I put a 100mVpp 100Hz sinewave, the circuit ouput 300mV (30Vpp square waves with 1Vpp at the input)
Sorry, I still have no idea wat your problem is.
Of course the various coils are galvanically isolated. And 2:1 is -6dB.
I think your measurement between 8 and 10 is wrong.
Do you have a scope? If so, ground pin 9 and hang a probe on 8 and 10 and see how they look on the scope (shown at the same time). Make a picture to show here.
Jan
Of course the various coils are galvanically isolated. And 2:1 is -6dB.
I think your measurement between 8 and 10 is wrong.
Do you have a scope? If so, ground pin 9 and hang a probe on 8 and 10 and see how they look on the scope (shown at the same time). Make a picture to show here.
Jan
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Thanks for your help.
This is scope measurements, the final ratio of all my tests circuits is always 1:2.
There are no waveforms between the Pin 9 and 10, when i ground the 9 pin there are two waveforms with an 1/2 amplitude (of the input coil signal) on the pin 8 and 10 (between 9 and 8 & between 9 and 8)
I can make a video if needed
I do not really know what your problem is (or what you think you detect as problem), but you can do an easy test to eliminate optional parts of the circuit, the ones doing higher order compensations.
You can short the + input of the opamp to the output ground, and see if your "problem" is always present.
Doing this is the equivalent of making the assumption that the transformer is (partially) perfect, which is not a great stretch.
If the problem subsides, it would be a good idea to document it in more details, symptoms, etc., to allow a more targeted help
You can short the + input of the opamp to the output ground, and see if your "problem" is always present.
Doing this is the equivalent of making the assumption that the transformer is (partially) perfect, which is not a great stretch.
If the problem subsides, it would be a good idea to document it in more details, symptoms, etc., to allow a more targeted help
Is it phase margin, phase reversal, or gain error?
Have you tried it in the op-amp circuit in post #1?
This transformer "requires" that specific op-amp connection. You can put in a very large signal, the op-amp cancels it, leaving very low flux in the transformer. That is how you get +30dB level for 8 bucks. While it should "work" as a simple transformer, it will overload very easy.
The dots on the diagram are quite odd. It is probably a copy of an older and more famous design. The original documentation may be more complete.
Have you tried it in the op-amp circuit in post #1?
This transformer "requires" that specific op-amp connection. You can put in a very large signal, the op-amp cancels it, leaving very low flux in the transformer. That is how you get +30dB level for 8 bucks. While it should "work" as a simple transformer, it will overload very easy.
The dots on the diagram are quite odd. It is probably a copy of an older and more famous design. The original documentation may be more complete.
I was lost because the unexpected high gain of the transformer and its circuitry was runing the whole circuit into extreme clipping levels (and i was seaching for a mistake that come from me
)The problem is the gain (1:2) because i must redesing the cricuit
(and therefore use a wrong circuit that should exhibit unpredictable performances)
Yes, i've built it 4 times and tested 6 different operational amplifier (two NE5532, two 5534 and two TL074) components were new each time.
It should satisfy me (especially for 8 bucks)
I'm able buy it to you (if you have it)
Pin 8,9,10 windings and your measurements are correct. As pin 8-10 are 0V it is seen just a resistor of winding DCR. The resistor is used positive feedback ratio which PFB cancels voltage drop of winding DCR of pin 6-7. This PFB reduces trafo distortion.
I still don't sure what your problem is. Have your previous build worked correctly? Was new one built correctly, especially around pin8,9(open),10 and noninverting input?
I still don't sure what your problem is. Have your previous build worked correctly? Was new one built correctly, especially around pin8,9(open),10 and noninverting input?
It was a mind blowing moment for me.
Can it be useful to adjust the resistor value of the positive feedback ?
I'm still very confused by the fact that this circuit is designed by the manufacturer with a -6dB gain
I've verified all my circuits (PCB and experimentation plates) and all of them are OK and shows the same result, the circuit amplify the signal instead of atttenuate it.
Your measurements on the transformer and the published application necessarily result in a 0.5 gain.
Any deviation is therefore caused by a material discrepancy between your build and the theoretical schematic.
Just be open-minded, it could be anything, especially the things you take for granted.
For example, if a 510 ohm resistor accidentally landed at the +in, it could have this type of effect; red and brown can easily be confused sometimes
Any deviation is therefore caused by a material discrepancy between your build and the theoretical schematic.
Just be open-minded, it could be anything, especially the things you take for granted.
For example, if a 510 ohm resistor accidentally landed at the +in, it could have this type of effect; red and brown can easily be confused sometimes
Input coil (2-4) =243.3Ω
Output coil (6-7) =294.6Ω
Output coil (8-10) =284.8Ω
Output coil (9-8) =146.1Ω
Output coil (9-10) =138.7Ω
Circuit resistors
R (linked to 6) =5.11KΩ
R (linked to 10) =5.09KΩ
Gain of 0.5 is reasonable.
External signals may be HIGH level. A typical push-pull "balanced output" from two opamps powered by +/-15V can hit 20V rms or +28dBu. This circuit's output can not exceed 10V or +22dBu. So a 6dB loss or 2:1 is correct if you must take "any" external signal.
Most signals are smaller. You may need gain. I would use your circuit, plus a potentiometer, plus a booster amp with gain of 2 to 10. Then very large sources can be turned-down, and very soft sources can be turned-up.
External signals may be HIGH level. A typical push-pull "balanced output" from two opamps powered by +/-15V can hit 20V rms or +28dBu. This circuit's output can not exceed 10V or +22dBu. So a 6dB loss or 2:1 is correct if you must take "any" external signal.
Most signals are smaller. You may need gain. I would use your circuit, plus a potentiometer, plus a booster amp with gain of 2 to 10. Then very large sources can be turned-down, and very soft sources can be turned-up.
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