Analog-to-digital converter based on voltage-controlled oscillator and method for improving linearity of analog-to-digital converter

The invention discloses an analog-to-digital converter based on a voltage-controlled oscillator, which comprises: an amplifier module used for changing an input analog signal voltage and outputting a current signal; a current copying module connected with the amplifier module and used for receiving the current signal and outputting a VCO bias current equal to the current signal; an analog-to-digital converter module based on current control which is connected with the current copying module and used for receiving the VCO bias current and outputting a corresponding digital signal, and the amplifier module comprises an input control circuit and a negative feedback amplifier circuit; the input control circuit is used for controlling an input analog signal voltage; and the inverted input end of the negative feedback amplifier circuit is connected with the input control circuit, a current signal is output according to a signal output by the input control circuit, and the normal input end of the negative feedback a