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
    can please help me and tell me what is collector and emitter feed back biasing
  2. PaulEE


    Dec 23, 2011
    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. :)