What is the maximum power transfer theorem?
The maximum power transfer theorem states that a source with impedance ZS = RS + jXS delivers maximum power to a load ZL = ZS* = RS − jXS. The power delivered then equals the available power |VS|²/(4RS) (VS rms).[1]
What does conjugate matching mean on a line?
With a lossless matching network, a conjugate match at one plane implies conjugate matches at every plane in the network. A conjugate match is not necessarily a reflectionless match to Z0: if the source is not Z0, standing waves may exist on the line while power transfer is still maximized.[1]
Does maximum power transfer mean maximum efficiency?
No. With a matched load, half the power is dissipated in the source resistance. Power amplifiers do not present a conjugate match to the transistor’s output; they present a load line that maximizes output power or efficiency within voltage and current limits.[2]
How does it relate to transducer gain?
Transducer gain GT = power delivered to load / power available from source. Simultaneous conjugate match on both ports of a two-port maximizes GT and is possible only if the device is unconditionally stable; the result is the maximum available gain. See gain definitions.[3]
Frequently asked questions
Is the source impedance of a PA 50 Ω?
The transistor's optimum load is usually a few ohms; the output network transforms 50 Ω to that value.
What is available power?
The maximum power a source can deliver, obtained into a conjugate match.
Does conjugate matching apply to antennas?
Yes; the receiving antenna delivers maximum power to a conjugate-matched receiver.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “Microwave Engineering, 4th ed.”. D. M. Pozar, Wiley. 2012.
- “RF Power Amplifiers for Wireless Communications, 2nd ed.”. S. C. Cripps, Artech House. 2006.
- “Microwave Transistor Amplifiers: Analysis and Design, 2nd ed.”. G. Gonzalez, Prentice Hall. 1997.