Large scale integrated circuit for converting pulse code modulated data

Abstract

In a digital-to-analog converter for converting a received digital signal having N bits and a sampling frequency fs to an analog signal; digital interpolation filter receives the digital signal and generates a modified digital signal having a number of bits less than N and a sampling frequency greater than fs, pulse width modulator receives the modified digital signal and generates a pulse signal having pulse widths which correspond to the modified digital signal, output buffer having a complementary metal oxide semiconductor (CMOS) inverter circuit including P channel and N channel transistors having respective resistance values receives the pulse signal and low-pass filter receives the output signal from the output buffer, wherein the digital interpolation filter, the pulse width modulator and the output buffer are formed in an integrated circuit, and when the transistors are conductive the resistance values of the P channel and N channel transistors are set equal to each other by adjusting a voltage applied to the integrated circuit substrate so as to improve the signal-to-noise ratio of the produced analog signal.