Transistor switch between positive and negative voltage

[trixtan]

Hi,
I am trying to find a way to switch on and off the current flow between positive and negative voltage rails using a third control voltage.
Please see the picture in attachment.
The voltage of V3 can be 3V or 0V. If V3 is high, current should be allowed to flow through R1. I was thinking about a relay, but maybe there is a better solution with transistors.
What is the best approach here? How would you do it?
Thank you

[Ian.M]

High side switch - PMOSFET or PNP transistor driven via a resistor from a low side NPN or NMOSFET controlled by the 3V signal.   If you use a PMOSFET, don't forget a 12V Zener to clamp the gate to keep Vgs within its max ratings.

[trixtan]

High side switch - PMOSFET or PNP transistor driven via a resistor from a low side NPN or NMOSFET controlled by the 3V signal.   If you use a PMOSFET, don't forget a 12V Zener to clamp the gate to keep Vgs within its max ratings.

Thank you Ian! I'll give a try, and see if it fits my application (i am trying to control the Mute of a LM3886 with those 3V).

[Ian.M]

Read the LM3886 datasheet - the mute function is NOT anything like the circuit you asked for.

You need to pull 1mA out of the Mute pin via the mute resistor which goes to the negative rail to enable the amplifier.  A SFH601 or other 100V Vceo optocoupler is the best bet.  Put its output side in series with the mute resistor with a 100K resistor from the phototransistor base to emitter to remove any leakage current from the base, and drive its input side via a 270R resistor from the 3V signal, cathode grounded.

[trixtan]

Thank you for the precious information, and for the solution.
I've looked  at the LM3886 datasheet, in particular to the equivalent schematic on page 7. From what I understand (but please correct me if I'm wrong) I have to "activate" that transistor which has the base grounded, and to do this I have to connect its emitter to a more negative voltage, which is the negative rail. Am I right?
Thank you

[Ian.M]

See LM3886 datasheet Page 2, Fig. 1.
The optocoupler's phototransistor output would connect in place of S1, collector to Rm.

You could try it without a pulldown resistor on the phototransistor base, but it only takes 5uA leakage current to start taking the amp out of mute mode. (See fig. 44).