Thread: transistor

it's considered that the transistor is a 2 port device....i.e having i/p terminal and o/p terminals.......so can u tell why the input impedance in case of common base configuration 24.4ohm...why isn't it any other value??

Originally Posted by avi108music

it's considered that the transistor is a 2 port device....i.e having i/p terminal and o/p terminals.......so can u tell why the input impedance in case of common base configuration 24.4ohm...why isn't it any other value??

According to this Wikipedia article on common base transistor circuit, the input resistance is 1/transconductance.
http://en.wikipedia.org/wiki/Common_base
According to this article on transconductance, it varies with the emitter current
http://en.wikipedia.org/wiki/Transco...ct_transistors

In summary, I don't know why it would always be 24.4.