Voltage Divider Bias: 4 Resistors, Base/Emitter, Collector, Stabilization?

[smart_worker]

why do we need 4 resistors?we are applying voltage across base emitter junction.Why do we need a resistor for collector side.One more thing how does the resistor across emitter provides stabilization?

 

[UltrafastPED]

A picture helps ...

 

[berkeman]

why do we need 4 resistors?we are applying voltage across base emitter junction.Why do we need a resistor for collector side.One more thing how does the resistor across emitter provides stabilization?

Please do some reading on your own first, and then if you have specific questions about that reading, you can ask them here. We prefer that you do some research/reading on your own before asking questions here.

Start with the intro article at wikipedia: http://en.wikipedia.org/wiki/Bipolar_transistor_biasing

.

 

[sophiecentaur]

why do we need 4 resistors?we are applying voltage across base emitter junction.Why do we need a resistor for collector side.One more thing how does the resistor across emitter provides stabilization?

This question is too vague for a definitive answer but I could say that you do not 'need' a collector resistor. The point is, though, that the transistor is an Amplifier, which controls the current through the collector by the signal on the base. If we are talking common emitter mode, then the collector current flows through a Load (to fulfil the purpose of it being an amplifier). That load does not have to be a resistor. It can be a loudspeaker, lamp, motor etc. etc. For analysing how the common emitter amplifier works basically, it's usual to use a Resistor because the calculations are more straightforward and you can just look at the voltage variation at the collector.

An emitter resistor provides feedback - but you need to read up some basic theory about amplifiers - as already suggested - and then about feedback (more advanced).