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Yes, Wiki maximum power transfer for more information.
Even for RF power amplifiers the impedances are only matched to the the characteristic impedance of the amplifier, not to the output of the amplifier which needs to have as low impedance as possible.
Nigel Goodwin said:No, the output stage is matched as well, and it's vitally important that it is - it's by far the most important matched stage in the transmitter. 50 ohm output impedance amplifier, matched to 50 ohm impedance coax, matched to 50 ohm impedance aerial - if any of the three isn't 50 ohms, extra circuitry is used to make them match.
No, the output stage is matched as well, and it's vitally important that it is - it's by far the most important matched stage in the transmitter. 50 ohm output impedance amplifier, matched to 50 ohm impedance coax, matched to 50 ohm impedance aerial - if any of the three isn't 50 ohms, extra circuitry is used to make them match.
Granted, between TX and ATU, it will be reasonably close to 50 Ω resisitive, but the point I'm making is not all transmission lines always need to be perfectly matched for maximum power transfer.
For MAXIMUM power transfer they do, but obviously in practice 'perfect' doesn't happen, and ACCEPTABLE power transfer doesn't require perfect matching.
The value of the output capacitor (1nF) is so small that it passes only radio frequencies to the 50 ohm load.
If its value is increased to 100uF and the value of the emitter bypass capacitor (10uF) also increased to 100uF then amplifier will have some gain.
The value of the base bias resistor (215k) for the output transistor is so high that the transistor is almost cutoff when it tries to have a current of 52mA into the 50 ohm emitter resistor. It should be about 6.8k ohms.
The input level is so high that the output clips the top and bottom.Hi Audioguru,
Attached are the simulation results of the circuit you modified. for a Vin of 10 mv and Frequency of 1K you see the signal clipped at the negative cycle
Then the output power to a 50 ohm speaker is only 0.00011W which is nothing.IC for the emitter follower cant be more than 3 mA.
An audio power amplifier uses two complimentary emitter-followers at the output (NPN and PNP) as a class-AB pair
Output impedance <50Ω
Output Swing ≤ 2V p-p
Max Supply Power = 15mW
How does the DC bias double the AC RMS power?You double the output power by having DC in the speaker instead of a resistor. Because a 50 resistor shunts the speaker 50. You can lose the blocking capacitor by direct drive speaker
How does the DC bias double the AC RMS power?