Re: Impedance mismatch or ...??


Matrix wrote:
Hello
When i connect the output of my circuit i.e. two Opamps feeding
differentials signals through a step up isolation transformer and onto
a twisted pair 75 Ohm impedance Bus. Then in loaded condition Signal is
attenuated to about 40% of original and distorted somewhat as compared
to unloaded condition. Signal is basically a bipolar +5V to -5V square
wave with a Rise/Fall time of about 150ns. Is it due to Impedance
mismatch or something else. Tranformer has an impedance of 4KO for
75KHz to 1MHz range of freq. Whats the solution to get rid of this
problem. Thanks.

Whoa! You said a mouthful.

First off, why are you using op-amps to handle a digital signal? That
doesnt make much sense.

Then you say you're using a step-up transformer. That doesnt make
sense either. Most op amps have output voltage and current ratios much
more suited for step-down transformer setup.

Then you say the transformer has 4K impedance. That's not the whole
story though, as transformers have an impedance ratio, not a fixed
impedance.


You may want to consider a complete redo. There are very nice
differential line driver IC's that do exactly what you need. See any
major IC maker web site.

.

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