Preamplifier design : Input and Load reflection coefficient

The preamplifier that I can trying to design is suppose to have a constant vswr that is suppose to be within certain nf limits. If I manage to figure out a load reflection coefficient value that would make the vswr fall with the required nf circle, that I will be able to design the matching networks. However, I am unable to do that. At that moment, I have managed to find the vswr circle using the input reflcetion coefficient relation. I would need to find the load reflection coefficient using this parameter and I am not sure how to do that. Or I may be approaching this problem in an incorrect way.

sthim2003

Reply to
sthim
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Are you simulating the design or are you building it. In case of the later you need to measure the stuff.

Input and output reflections are independent of each other, at least from a certain complexity up. That is the point of an amplifier, to decouple input from output.

Rene

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Ing.Buero R.Tschaggelar - http://www.ibrtses.com
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Reply to
Rene Tschaggelar

Try searching google for an app note from Motorola or HP on Small Signal Amplifier Design Linvill Method or some combination of those words.

What transistor is it? Doesn't the spec sheet give a bias point and input reflection coefficient (not a vswr circle) for optimum NF?

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Best Regards,
Mike
Reply to
Active8

S12 is never 0. Design equations for simultaneous I/0 match are available.

Reply to
Precious Pup

Splitting hairs ? I said it was dependent on the complexity. A standard OpAmp with sufficient gain, sufficient feedback has no coupling between the two. It ideally has infinite input impedance, zero output impedance and with some external parts can be made to match whatever on both sides independently.

Sure, a single transistor looks a bit different.

Rene

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Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
Reply to
Rene Tschaggelar

I am only simulating it at the moment. I am going to use a Agilent ATF series PHEMT.

sthim2003

Reply to
sthim

Not really.

He is likely talking about an RF/microwave preamp. He didn't mention an op-amp.

yeah, a "bit."

Reply to
Precious Pup

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