hello,everyone.
consider a very simple circurt.
if Vbc of a npn transistor is zero and Vbe is 5V,how much is each current of the bjt?
I used the following formula.
let
Icc = IS[exp(qVbe/kT)-1]
Iec = IS[exp(qVbc/kT)-1]
Ict = Icc - Iec
then
IE = -Ict-Icc/BF
IC = Ict-Iec/BR
IB = Icc/Bf+Iec/BR
where
IS is the saturation current and value is 2e-16
BF is the forward beta and value is 200
BR is the reverse beta and value is 0.1
so i calculated:
let q/kT = 25mv then qVbe/kT is 200
exp(200) = 7.22597377e86(sucn a huge number)
exp(200)-1 is almost the same value = 7.23e86
Icc = 1.446e81
since Vbc = 0,Iec = 0
Ict = Icc-Iec = Icc
so i concluded:
IE and IC is almost 1.446e81 which seemed impossible(too huge).
so,what am i doing wrong?
thanke you.
consider a very simple circurt.
if Vbc of a npn transistor is zero and Vbe is 5V,how much is each current of the bjt?
I used the following formula.
let
Icc = IS[exp(qVbe/kT)-1]
Iec = IS[exp(qVbc/kT)-1]
Ict = Icc - Iec
then
IE = -Ict-Icc/BF
IC = Ict-Iec/BR
IB = Icc/Bf+Iec/BR
where
IS is the saturation current and value is 2e-16
BF is the forward beta and value is 200
BR is the reverse beta and value is 0.1
so i calculated:
let q/kT = 25mv then qVbe/kT is 200
exp(200) = 7.22597377e86(sucn a huge number)
exp(200)-1 is almost the same value = 7.23e86
Icc = 1.446e81
since Vbc = 0,Iec = 0
Ict = Icc-Iec = Icc
so i concluded:
IE and IC is almost 1.446e81 which seemed impossible(too huge).
so,what am i doing wrong?
thanke you.