# charge pump help need

#### hertz.12

Joined Apr 25, 2015
41
hi
i want step up voltage from 3.3v to 6v...so i made charge pump but i put 2222 transistor instead of diode...now every thing work fine and i have 6.1 volt ..no problem with circuit...but i am afraid that the transistor may be damage because the "Emitter-Base Breakdown Voltage = 5v" i am really don't understand what Emitter-Base Breakdown Voltage are???

here is my circuit

#### WBahn

Joined Mar 31, 2012
30,034
Emitter-base breakdown voltage is exactly what it says. If the emitter-base voltage exceeds 5 V, then it may break down and start conducting current.

jjw

#### hertz.12

Joined Apr 25, 2015
41
so i have to put Schottky diode between the transistor and the cap to protect the Emitter from exceeds 5 V

sure?
it works fine now and nothing happen to 2n2222

thanks

#### WBahn

Joined Mar 31, 2012
30,034
At what point does Veb exceed 5V now?

Have you looked closely at your output voltage on a scope?

#### hertz.12

Joined Apr 25, 2015
41
hi
i don't have a scope....voltmeter only

#### crutschow

Joined Mar 14, 2008
34,394
Put the diode in series with the base.
That way you will still protect the emitter but won't reduce the output voltage.

#### hertz.12

Joined Apr 25, 2015
41
Put the diode in series with the base.
That way you will still protect the emitter but won't reduce the output voltage.
and the emitter will not damage? that will protect it for sure?

#### jjw

Joined Dec 24, 2013
823
I don't understand how the circuit could work, the base is floating and the transistor never conducts.
Is the diagram correct ?
What is the 20Hz voltage on the base ?

Edit: Forget the former sentence about the base, but this circuit won't charge or pump

Last edited:

#### jjw

Joined Dec 24, 2013
823
To double the voltage, Q1 must be a PNP transistor, emitter to +3.3V, from collector a diode to another capacitor, the base voltage pulsing from 0 to 3.3V.

#### crutschow

Joined Mar 14, 2008
34,394
and the emitter will not damage? that will protect it for sure?
Yes.