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Old 18th August 2015, 08:27 PM   #1
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Default Output Resistors in P3A amp

Hi guys,

I am building a P3A amp from bits I have laying around, however I only have 0.22ohm resistors not 0.33ohm that is used in the design.

Will I need to change the value of other components to match or should 0.22ohm be fine?

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Old 18th August 2015, 09:27 PM   #2
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That should be fine, don't forget when working the quiescent current, the voltage drop will be a different reading than published.
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Old 18th August 2015, 10:27 PM   #3
sreten is offline sreten  United Kingdom
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Nope. Reducing emitter resistors increases optimum bias
current and barely changes the emitter voltage drop.

As it is the P3A is very waffly about optimum bias.

See D.Self regarding alleged CFP optimum bias.

For sure the P3A has Gm doubling @ 50ma to 100ma.

But with such a wide range of bias, 20mA to 100mA,
emitter resistor values don't matter too much at all.

rgds, sreten.
There is nothing more practical than a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
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