Maximum voltage that can be applied across NPN transistor Base and Emitter.

ku637

Advanced Member level 4

What is the maximum input voltage we can apply at input?
I see vebo spec some 6V in data sheet but considering 10k the current will be limited.
But how to identify the limiting scenario voltage?

KlausST

Super Moderator
Staff member
Hi,

V_BE or V_EB or voltage at "input"?

These are different three things ...you talk about all three, this is confusing.

Klaus

Last edited:

ku637

Points: 2

betwixt

Super Moderator
Staff member
If its a positive voltage, the maximum voltage will be determined by the rated base current or the power rating of the series resistor, whichever comes first.
If it's a negative voltage, it will be twice (because it is halved by the potential divider) of the transistors BE breakdown voltage.

Brian.

ku637

Points: 2

Advanced Member level 3
Be carefull about Emitter Base breakdown, some small signal parts will suffer noise performance changes
and other parameters when E-B experiences breakdown. This can be a permanent change in device per-
formance.

Regards, Dana.

ku637

Points: 2

ku637

Advanced Member level 4
Sorry for the confusion. I understand.. I was checking primarily the safe voltage at input.

Suppose I apply 10V at input the divider presents 5V to the Base Emitter junction but since Base Emitter is ON the voltage developed across the base emitter is approximately 0.7V the current is limited by 10k and it will be 1mA base current I guess. And i assume then the power dissipation 1mAx 0.7V + Ic x Vce will be the limiting parameter.

dick_freebird

Advanced Member level 5
Reverse bias E-B overstress induces hot-carrier charging
of junction-adjacent oxides which creates and/or exposes
traps (noise) and charges them (Vbe drift, low current

A limit of 6V is meant to leave margin relative to the
actual breakdown (typ 7-8V in a medium voltage
vertical BJT).

stenzer

Advanced Member level 2
Hi,

the current flowing into the base is (10 V - V_BE)/(10 k) $\approx$ 1 mA. Unfortunately the maximum base current is usually not specified in the datasheet. If you perform a websearch regarding the maximum base current you will find different values, here you can find values from a semiconductor manufacturer [1].

[1] https://www.rohm.com/products/faq-search/faqId/231

BR