# pnp- junction ( transistor ) question ?

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#### rabso

##### Newbie level 4
how transistor amplifies the current when I(emitter) = I (base)+ I(collector) , do the mean by amplifying is controlling the current like the current in circ. is 10 A and then reduce it to 5 and then amplify it to 10 again ?

#### LvW

Amplifying in BJT transistors is by Beta factor (B)
Ic= B * IB
IB the base current
Ic the collector current
B Beta factor

GOOD LECTURE NOTES AVAILABLE WITH EXAMPLES
http://whites.sdsmt.edu/classes/ee320/notes/320Lecture11.pdf
Hi Mahmoud, congratulation to the good lecture notes.
Contrary to many books and internet publications (and also in contrast to your own wording) the transistor is treated in this note as a voltage-controlled device (which is the physical truth).
The relation Ic=B*beta is NOT used to verify amplification but only to calculate the (unavoidable) base current IB=Ic/beta.
(see the discussion regarding current or voltage control of the BJT we had in this forum some days ago)

#### Junus2012

the transistor is only control element it will provide the amplification by scaling the input current from the power supply. it mean that the amplification is converting the D.C power in to an A.C power with a certain efficiency.
when you use the bipolar as a voltage amplifier then the input is base and the output is the collector so you get difference in current of factor beta

how transistor amplifies the current when I(emitter) = I (base)+ I(collector) , do the mean by amplifying is controlling the current like the current in circ. is 10 A and then reduce it to 5 and then amplify it to 10 again ?

#### rabso

##### Newbie level 4
the transistor is only control element it will provide the amplification by scaling the input current from the power supply. it mean that the amplification is converting the D.C power in to an A.C power with a certain efficiency.
when you use the bipolar as a voltage amplifier then the input is base and the output is the collector so you get difference in current of factor beta
beta is never bigger than one so ib when multiplied be beta it will decrease .

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but i found that is used to separate two circuits so the current begin one the first circ on low r and goes to another circ with big r ( r = resistor )

#### FvM

##### Super Moderator
Staff member
beta is never bigger than one
Beta is usually in a range of several 10 up to many 100.

#### Junus2012

I dont know who told you that B=1 ??????????? it is in order of tens

beta is never bigger than one so ib when multiplied be beta it will decrease .

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but i found that is used to separate two circuits so the current begin one the first circ on low r and goes to another circ with big r ( r = resistor )