1. If the power supply of the circuit is a linear power supply, a low-voltage sine wave signal can be obtained from the output of the power transformer and divided by a resistor to an acceptable amplitude for the subsequent circuit. Otherwise, a single transformer is used to turn 220V into a low-voltage signal.

If the 220V grounding is reliable, the live wire can be directly divided by resistors to obtain low-voltage signals.

2. As shown in the figure below, the low-voltage sine wave signal (U0) is converted into a square wave signal (U 1) with the same frequency by a hysteresis comparator, and the square wave signal is converted into a triangular wave signal (U2) with the same frequency by an integrator.

3. Design a 64V DC power supply, and use a triode amplifier circuit to amplify the triangle wave signal.