a doubt regarding saturation mode of BJT

[dexterdev]

Hi all,
I have a doubt regarding saturation mode of BJT. Saturation occurs when both emitter-base junction and base-collector junction gets forward biased. For forward biasing a silicon p-n junction only 0.7V is needed. So is for emitter-base junction. But not for base-collector junction. Because we know at saturation voltage across collector and emitter Vce is 0.2V. Using Kirchoff's voltage laws the voltage at base-collector p-n junction is less than 0.7V. Why is it lesser?

-Devanand T

 

[unclejed613]

google is your friend....
https://www.physicsforums.com/showthread.php?t=401308

 

[audioguru]

Did you look at datasheets for the "(maximum) Collector-Emitter Saturation Voltage"? Then the base current is 1/10th the collector current (for most small American transistors) so the transistor is turned on very hard.

When a 2N3904 transistor is saturated with a collector current of only 50mA and a base current of 5mA then the maximum base-emitter voltage is 0.95V, not just 0.7V so of course the collector-base junction is forward biased.

 

[dexterdev]

thankyou for replies