Patent ID: 6891495

Claim:
An analog-to-digital converter, comprising: a plurality of analog-to-digital converting units connected in serial, each analog-to-digital converting unit comprising: a current comparator having a current input terminal for receiving a sampling current, a reference current input terminal for receiving a reference current and a bit output terminal for outputting a bit signal; a current operation circuit having a current output terminal for outputting a compared current according to the sampling current and the reference current, and an operation controlling terminal for receiving the bit signal; and a first controlling terminal for receiving a clock signal to latch the bit signal, wherein the analog-to-digital converting units output the bit signals in sequence in a period of the clock signal, wherein the bit signal is at a high voltage level when the sampling current exceeds the reference current, and the bit signal is at a low voltage level when the reference current exceeds the sampling current; and a digital-to-analog converter comprising a plurality of current mirrors and second switches coupled to the current mirror for receiving the bit signal to generate a return current to be tested, wherein at least one current mirror generates a current corresponding to the bit signal according to the reference current.