Output Power PP AB Stage - Value of Emitter Resistor for thermal Bias Stability - diyAudio
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Old 29th November 2010, 10:08 PM   #1
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Default Output Power PP AB Stage - Value of Emitter Resistor for thermal Bias Stability

Output Power PP AB Emitter Follower stage - Value of Emitter Resistors without necessary Vbe multiplier or diode against thermal runaway

Bob Cordell Interview: BJT vs. MOSFET
I don't find the appropriate informations.

How I calculate the smallest possible value of emitter resistor in a push pull output power stage without necessary Vbe multiplier, NTC resistor or diode for thermal compensation ? Both for normal and Sziklai darlington (CFP).

From a certainly minimum resistor value this emitter resistor serves even for an excellent thermal bias stability. The value must be higher than 1 ohms (below 1 ohms Vbe multiplier transistor absolutely necessary), but lower than 100 ohms - so I think.
If I know this value, I can use only a bias resistor like topologies with audio lateral mosfet's in the output.
I think, this resistor value is also dependent from the wished value of idle current through the output.

Thank you for your comments.

Last edited by tiefbassuebertr; 29th November 2010 at 10:15 PM.
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Old 30th November 2010, 02:40 PM   #2
AndrewT is offline AndrewT  Scotland
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the Cordell link takes you to the correct Thread for the local Thermal Stability.
See post2276 and beyond for the details.
This is explained in his book. Have you bought it yet?

The first link is for overall Thermal Stability.
regards Andrew T.
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