what is collector and emitter feed back biasing

Discussion in 'General Electronics Chat' started by placide, Jan 21, 2012.

  1. placide

    Thread Starter New Member

    Oct 1, 2011
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    0
    can please help me and tell me what is collector and emitter feed back biasing
     
  2. PaulEE

    Member

    Dec 23, 2011
    423
    32
    Collector biasing involves connecting a resistor directly from the collector to base. This is also referred to as "self-biasing". If you sketch a simple transistor circuit with a collector resistor to V+ and emitter resistor to V-, and then put the collector-to-base resistor in, think about what happens when the temperature (beta, Vbe, etc.) values change in the transistor...

    Conductivity in the base-emitter junction increases, beta may rise, more current from collector to emitter flows. More current flow implies that the transistor will drop a lower voltage; this in turn is "fed back" to the base in the form of negative feedback, thus, re-establishing the original bias point.

    The emitter resistor does something similarly. More current flows -> voltage drop on emitter resistor -> less voltage toward the top of the circuit -> more stable over temperature.

    Anyone want to critique my analysis? I'm a bit rusty on discrete transistor stages.

    Hope that helps. :)
     
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