Positive voltage into emitter of a transistor

Looking at using a couple of 2n2222 transistors in an unusual way which might cause the emitters of said transistors to have a positive voltage, about 6 volts and 100 to 150Ma, applied to them. Will I blow out my transistors without throwing some diodes into the mix?

Ultimate goal here is to control a 2 wire full rotation servo in both directions using 4 arduino pins and 4 transistors and switching output in the right order.


and 100 to 150Ma

Wow :astonished: I hope it is a typo and you only have 100mA

You seem to be confused as you can only apply a voltage you can't apply a current to a situation.

Please draw the schematic.

The data sheet says that transistor has an emitter base reverse breakdown of 6v so you are in trouble.

Sorry, this is all new to me so I’m learning.

Maybe I should have said “forward” voltage into the emitter, not positive.

Anyway, once I drew out what I had in my head it turns out there wouldn’t be a positive or forward voltage into any emitter. Schematic attached and here is the sudo code…

Rotate first direction
set pin 5 high
set pin 6 low
set pin 7 low
set pin 8 high

Rotate second direction
set pin 5 low
set pin 6 high
set pin 7 high
set pin 8 low

Just was killing time on the train and wondering if this would work.


1.21gigawatt / a few thousand volts of the thunder bolt = about 100MA of current. You know where I'm going? :grin:

A diagram and what you want the circuit to do will be helpful.

What you are drawing is a H-bridge circuit. Normally these are made with complementary transistors (PNP and NPN) like this:-

There are problems with using all NPN transistors, namely turning on the top transistor.

Thanks both. Glad to know I was at least on the right track-ish. Was just thinking out the circuit in my head on the train this morning.

KE7GKP, by "servo" It's your basic servo style housing but I guess it would really be considered a gear reduced motor. It only has 2 leads, red and black. Give it power one way and it goes clockwise. switch it and it goes counter-clockwise.