What is the circuit for the Singing doll that start when touching hands
It will probably be an a.c. voltage applied to the metal contacts so that it can capacitively couple through the skin, rather than having to have a high impedance d.c. input that will be subject to spurious triggering problems. As such, it could employ sporadic pulses, since the triggering does not have to happen extremely rapidly after the contacts are closed. For example, a 1µs pulse could be generated every 100ms, for a duty cycle of 0.001%. This will allow the average power dissipation to be reduced by the same factor.