# 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.

Thanks.

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.

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.