# A curiosity

Discussion in 'General Electronics Chat' started by bc108, Jul 19, 2010.

1. ### bc108 Thread Starter New Member

Jul 18, 2010
10
2
Not usefull, but a curiosity.

Generate -.5 volts or so from a positive 9v or more dc supply with one npn transistor (bc108, 2n2222 etc) and one resistor:

Ground transistor base, connect resistor between emitter and +ve rail, aim to draw about 10ma when the emitter base junction avalanches at about 7v. (emitter base junctions break down at quite low reverse biases). Measure voltage between ground and collector. It's negative!, where did that negativity come from?.

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
I saw this and moved it where it can get more commentary.

May 11, 2010
241
38
whoa, that's an excellent trick!

what's happening? some sort of electron pump?

4. ### eblc1388 Senior Member

Nov 28, 2008
1,542
102
Let's say we try the experiment with a 9V battery.

If the the collector is negative w.r.t ground, then the total voltage between +9V and collector will be larger than 9V.

So you have created 9.5V from a 9V battery with just a transistor and one resistor, provided the experiment can be repeated.

Then you might connect this 9.5V to just another similar setup and get 10V....

5. ### Syniva New Member

Jun 21, 2010
25
0
So does anyone know how this works?

It kind of reminds me of an oscillator I once made. I was trying to use as few components as possible, and eventually ended up with just a transistor and a capacitor and maybe a resistor. One of the transistor leads wasn't even attached to anything. I think it required 12 volts to work, and wouldn't do anything with only 5 volts. Unfortunately, I don't remember how to wire it together, and trying every way I can think of fails to turn up a circuit that does anything.