Turning a "switch" off when voltage present

For a project I’m working on, I want to be able to turn a “switch” (eg, a transistor) off when a voltage is present in another part of the circuit.

Is there a way of doing this?


Problem solved: nand gate

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Hi Kevin, yep, all you need is some inverting logic. That could look like a NANA gate, however, if you’re already working with NPN transistors, then you can just drive the base of your primary switch with another transistor and a pullup resistor to invert the logic.

That might be simpler than a larger logic-gate package.