As the scaling of CMOS technology advances, the characteristics of transistors are evolving toward digital circuit design. This means conventional analog design techniques are getting harder to apply to advanced technology, because of the low power supply voltage, narrow dynamic range of switching properties, and low trans-conductance of transistors. Despite such circumstances, analog-to-digital converter (ADC) performance is still advancing, thanks to innovative new architectures. This paper reviews the recent trend of ADCs, exploring their performance as well as use of the time interleave scheme, non-static current amplifiers, and hybrid architectures.