Converter

[EAUX]

how would u modify this circuit with minimum components to give 0 to -22vdc output @ IO2 by the actuation of s1?

Thanks in advance.

[pebe]

Have you got your circuit right? because you have the emitter of the 2N2222 going to a symbol 'VCC'.

When SI is at the 'ground' position the transistor is already in conduction and saturated, and switching an extra 5V to point 101 will provide even more base current. So there is no way you can get the transistor to switch on and off with that circuit.

One way would be to connect point 101 to ground and connect S1 between the base and emitter of the transistor.