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A double chopper-stabilized analog front-end(DCS-AFE) circuit for a thermopile sensor is presented,which includes a closed-loop front-end amplifier and a 2nd-order 1 bit quantization sigma–delta modulator. The amplifier with a closed-loop structure ensures the gain stability against the temperature. Moreover, by adopting the chopper-stabilized technique both for the amplifier and 2nd-order 1-bit quantization sigma–delta modulator,the low-frequency 1/f noise and offset is reduced and high resolution is achieved. The AFE is implemented in the SMIC 0.18 m 1P6M CMOS process. The measurement results show that in a 3.3 V power supply, 1 Hz input frequency and 3KHz clock frequency, the peak signal-to-noise and distortion ratio(SNDR) is 55.4 dB, the effective number of bits(ENOB) is 8.92 bit, and in the range of –20 to 85 degrees, the detection resolution is 0.2 degree.
A double chopper-stabilized analog front-end (DCS-AFE) circuit for a thermopile sensor is presented, which includes a closed-loop front-end amplifier and a 2nd-order 1 bit quantization sigma- delta modulator. -loop structure ensures the gain stability against the temperature. Furthermore, by adopting the chopper-stabilized technique both for the amplifier and 2nd-order 1-bit quantization sigma-delta modulator, the low-frequency 1 / f noise and offset is reduced and The measurement results show that in a 3.3 V power supply, 1 Hz input frequency and 3 kHz clock frequency, the peak signal-to-noise and distortion ratio ( SNDR) is 55.4 dB, the effective number of bits (ENOB) is 8.92 bit, and in the range of -20 to 85 degrees, the detection resolution is 0.2 degree.