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Why we put a resistor or other component in collector side of BJT transistor?

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jandreas

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hi... i wanna ask you people about BJT transistor, mabe it's a simple uestion.. but honestly i dont' know the answer. the question is " why we put a resistor or other component in collector side , no on emitter side?? and some people answered 'coz the current in collector side bigger in emitter, is it true??? but from the book that i read, IE=IB+IC, so i thinked the current in emmiter side is bigger than the collector..This is really make me confuse.. is there anyone can help me with great answered in theorical and formula... pleasssthank you

RGDS jandreas
 

HELP BJT transistor

i think u r talking about base baise configuration or switch configuration of bjt,reason is that we put a load on collector to get output,in emitter follower configuration we insert a resistance between emitter and ground but still we have a resistance on collector for the same reason that we are getting output from there,or reply me with any new question regarding this we can discuss it further
 

Re: HELP BJT transistor

What we often want from an amplifier is to have a voltage input and a voltage output. When you draw the small signal diagram of a BJT (or any transistor) you can see that, from a small-signal point of view, it's basically a voltage-to-current amplifier, or a transadmittance-amplifier. However, if we want to convert the resulting output current into an output voltage, the simplest thing we can do is to present an impedance to this current, and measure the resulting change in output voltage. In this case we created a voltage at the output, as we wanted. Hope this helped you!
 

Re: HELP BJT transistor

Good explanation !
Some words regarding resistor in the emitter path:
The same explanation applies also for a resistor between emitter and ground (resp. neg. supply). Thus, the emitter current is converted to an emitter voltage.
However, the effect of this resistor Re is quite different if compared with the collector resistor: The created emitter voltage reduces the voltage between base and emitter (this effect is called negative feedback) and the voltage gain related to the emitter output is reduced to a value<1.
 

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