OP-AMP pulse circuit with DC offset

Phil;

According to the OPA547 data sheet its Absolute Maximun power supply voltage is 60V. Your 26V + 54V = 80V.

You could use a single +60V supply and use the OPA547 input to generate the 24V offset voltage at its output.

Phil;

Your negative supply is +26V, not -26V?

Phil;

Without the positive sign I assumed that it was -26V.

1. Can you post (attach) your TINA circuit file?

I have attempted to upload the file.  This is my first try.

Phil;

Shouldn't the feedback go to the op amp inverting input?

This is the non-inverting version.  Both work according to the simulator.  I don't seem to get the same rising and falling edge response but the simulator still says this is a valid circuit capable of diving a 50VDC 1ms pulse.

I can't use the second version of this design because our function generator can't supply a negative pulse and would require more circuitry.  Also notice the polarity of the pulse generator in the second design.

Phil,

The first circuit that you call "inverting" is connected as a comparator--positive feedback with hysteresis. I don't think this is what you intend. This op amp is not suited to operation as a comparator.

Another troubling aspect of your circuits is that the signal generator is ground referenced. It is pulling the op amp input below its V- supply pin voltage (outside the valid common-mode range). This is not a valid region of operation and the macromodel may not behave the same as the actual hardware. It could also damage the device, though the series resistors should protect it.

Perhaps if you describe more about your intended application we could suggest a possible circuit.

Regards, Bruce.

Yes, the second circuit is not the way to go.  The first circuit I posted is the target.  Run the TINA tool using the Transcient analasis and the graph it generates is what I am trying to do.  I have also posted the objective in the opening post.  I use these circuits all the time except I have never done a DC offset version.

How about this circuit?  It is a summing Amplifier.

Phil,

This latest circuit (summing pulse circuit.TSC) seems to make sense. It is actually using the op amp as an op amp.

For your reference, the circuit driving the inverting input with feedback to the non-inverting input is using the op amp as a comparator. Output voltage swing, would be controlled only by the power supply voltage of the op amp as it is slamming rail-to-rail. It is not a recommended mode of operation for most op amps and macromodels could very likely to be inaccurate.

The second circuit is flawed because the input voltage is not level-shifted to within the input common-mode range of the op amp. Again, macromodels may not properly predict behavior when mistreated this way.

Regards, Bruce.

Thanks for all the assistance.  I am never to old to learn (yet).  I am having our technician modify the circuit.  If I do not return I am on to the next fire someone has.