base or fixed bias

Thread Starter

amaresh92

Joined Oct 31, 2010
23
i wonder if anyone could tell me the working of base bias in detailed.i am not able to understand it.
advanced thanks.
 

Audioguru

Joined Dec 20, 2007
11,251
A transistor needs base current for it to turn on. But transistors even with the same part number have different amounts of current gain and different amounts of base-emitter voltage so a voltage divider is used to feed bias current to the base and an emitter resistor is used to reduce the variations among transistors.
 

Thread Starter

amaresh92

Joined Oct 31, 2010
23
A transistor needs base current for it to turn on. But transistors even with the same part number have different amounts of current gain and different amounts of base-emitter voltage so a voltage divider is used to feed bias current to the base and an emitter resistor is used to reduce the variations among transistors.
how does base currrent remains constant and what makes it to be constant?
thanks.
 

Audioguru

Joined Dec 20, 2007
11,251
If the supply voltage is regulated then the voltage divider feeding the base and the emitter resistor make the base-emitter current constant.
 
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