A non-isolated power supply. A positive power and a negative power are respectively formed by charging a +VCC1 energy storage filter and a ?VCC2 energy storage filter connected in series and discharging the +VCC1 energy storage filter 102 and the ?VCC2 energy storage filter. The output positive and negative power may be differently combined by changing the capacities of the +VCC1 energy storage filter and the ?VCC2 energy storage filter and may be equal or unequal.

An amplifier circuit including an input amplifier, an output amplifier and a diode device is provided. The output amplifier is coupled to the input amplifier and outputting an output voltage. The diode device is coupled between an output end and an input end of the output amplifier. When a voltage difference between the output end and the input end of the output amplifier is greater than a barrier voltage of the diode device, the diode device is turned on, and an overshoot of the output voltage is reduced. The diode device includes a variable resistor to increase the barrier voltage of the diode device.