In this paper, a CMOS analog-to-digital converter (ADC) with a 6-bit 100MSPS at 1.8V is described. The architecture of the proposed ADC is based on a folding type with a resistive interpolation technique for low power consumption. To reduce the power consumption, a folder reduction technique to decrease the number of folding blocks (NFB) by half of the conventional ones, an averaging folder technique, and a compensated resistive interpolation technique are proposed. Further, an autoswitching encoder for efficient digital processing is also presented. With the clock speed of 100MSPS, the ADC achieves an effective resolution bandwidth (ERBW) of 50MHz, while consuming only 4.5mW of power. The measured result of figure-of-merit (FoM) is 0.93 [pJ/convstep]. The active chip occupies an area of 0.28mm² in 0.18μm CMOS technology.