A low-power 2nd-order CT delta-sigma modulator with a single operational amplifier

We present a 2nd-order 4-bit continuous-time (CT) delta-sigma modulator (DSM) employing a 2nd-order loop filter with a single operational amplifier. This choice strongly reduces the power consumption, since operational amplifiers are the most power hungry blocks in the DSM. The DSM has been implemented in a 65 nm CMOS process, where it occupies an area of \(0.08\,\hbox {mm}^2\) . It achieves an SNDR of 64 dB over a 500 kHz signal bandwidth with an oversampling ratio of 16. The power consumption is \(76\,\upmu \hbox {W}\) from a 800 mV power supply. The DSM figure-of-merit is 59 fJ/conversion. The CT DSM is well suited for the receiver of an ultra-low-power radio.