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hey audioguru,can you tell me how did you calculate the i/p impedence of heros amp.i mean you cal the i/p impedence of the ce amp and then how did you calculate the ab amps i/p impedence and what about the o/p impedence of the ce amp cuase it is also seen by the power amp.
hey audioguru,can you tell me how did you calculate the i/p impedence of heros amp.i mean you cal the i/p impedence of the ce amp and then how did you calculate the ab amps i/p impedence and what about the o/p impedence of the ce amp cuase it is also seen by the power amp.
I just guessed. In the simulation the input impedance is 1360 ohms.
The input impedance of a common-emitter transistor is hFE times its internal re plus hFE times its RE, then any biasing resistors in parallel.
The internal re of a silicon transistor is 0.026/emitter current in milliamps.
The output impedance of a common emitter transistor is its collector resistor. The transistor itself is a current-sink with a very high impedance. Negative feedback from the output to the input reduces the input impedance and reduces the output impedance.
The output impedance of Hero's amplifier is so low that it cannot be measured on the simulation. Most good power amplifiers have an output impedance of 0.04 ohms or less at low frequencies.
Bootstrapping an an amplifier's driver transistor allows it to have a much higher voltage swing and have much less distortion.
The bootstrapping capacitor drives the driver transistor's bias resistor above the power supply voltage so the transistor continues to have enough base current when the signal at its base goes positive.
I stayed away from the forum for some months, due to severe lack of time.
But I carefully read all, and I'd like to thank all people who posted.
I'll be trying to design a better amplifier these days, and hope I works fine this time!
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