Application of a switch-type comparator in 4-b flash ADC

The design and optimization of a comparator with two transistors are presented. In this paper, a simple comparator without using an op-amp is proposed. It only uses the principle of the effect of back-gate bias on MOSFET. This switch-type comparator is tested in a flash ADC. By adjusting the different voltages of back-gate bias on MOSFET, the switch-on voltage of comparator can have a linear variation, compare the input analog signals with reference voltages. Then their results are encoded to the digital signal. This type of converter has no offset and gain errors in addition to being highly linear. A further advantage is the small amount of circuitry is required in its implementation and high speed IC with high speed is expected in a future study.