How to improve Power Gain!? Is S21 equal to Power Gain?

jeffreyedaboard

the S21 is a ratio of energy and not power. So if you are work in a matched world, the answer is yes, they are the same, but if you work in un-matched condition the answer is no, they are not the same.

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Thanks , dinone , but i design a diff-LNA, the s21 is 13db, i tried many methods to improve it , but it seems to be limited!

Added after 1 minutes:

and what is the limite!?

The S21 measurement is based on a reference impedance, usually 50 ohms. The source and load impedance as seen by the circuit can be changed with LC-transmission line circuits to values that may possibly increase the gain and reduce the noise figure.

The standard textbooks tell you how to do this.

thanks flatulent !
but i tried to improve the s21 with LC loading again and again , but the results change not so much , s21 stays at 13db!

AT higher frequencies 13 dB of gain is quite respectable. Try putting two of these stages in a row (tandem) if you need more gain.

thanks flatulent very much!