I want to command a 12V DC motor with the output of a clock alarm
Something like this might work for your application:







simulate this circuit &ndash; Schematic created using CircuitLab

Q3 serves as a class-C amplifier that generates a 12V waveform at a higher current (if it was unloaded) which then goes through a peak-detector that drives a switch transistor (Q1).

I put some guesses at what were the impedances of the alarm drive signal and the motor, and a 2N3904 to drive a motor is probably not a good choice, but you should get the idea.

If you use a low-threshold NFET as the drive transistor you should be able to simplify some of the circuitry, but 1Vpp does not leave much room to work with.

Looking at it more carefully, if you remove R3 and D3 the circuit would still work.







simulate this circuit