This paper presents a fully differential third-order (2-1) switched-current (SI) cascaded delta-sigma modulator (DSM), with an analog error cancellation logic circuit, and a digital decimation filter that is fabricated using 0.18-µm CMOS technology. The 2-1 architecture with only the quantizer input being fed into the second stage is introduced not only to reduce the circuit complexity, but also to be implemented easily using the switched-current approach. Measurements reveal that the dominant error is the quantization error of the second one-bit quantizer (e2). This error can be eliminated using an analog error cancellation logic circuit. In the proposed differential sample-and-hold circuit, low input impedance is presented with feedback and width-length adjustment in SI feedback memory cell (FMC); and that a coupled differential replicate (CDR) common-mode feedforward circuit (CMFF) is used to compensate the error of the current mirror. Also, measurements indicate that the signal-to-noise ratio (SNR), dynamic range (DR), effective number of bits (ENOB), power consumption and chip size are 67.3 dB, 69 dB, 10.9 bits, 12.3 mW, and 0.200.21 mm2, respectively, with a bandwidth of 40 kHz, a sampling rate of 10.24 MHz, an OSR of 128 and a supply voltage of 1.8 V.

This work develops a third-order multibit switched-current (SI) delta-sigma modulator (DSM) with a four-bit switched-capacitor (SC) flash analog-to-digital converter (ADC) and an incremental data weighted averaging circuit (IDWA), which is fabricated using 0.18µm 1P6M CMOS technology. In the proposed DSM, a 4-bit SC flash ADC is used to improve its resolution, and an IDWA is used to reduce the nonlinearity of digital-to-analog converter (DAC) by moving the quantization noise out of the signal band by first-order noise shaping. Additionally, the proposed differential sample-and-hold circuit (SH) exhibits low input impedance with feedback and width-length adjustment in the SI feedback memory cell (FMC) to increase the conversion rate. A coupled differential replicate (CDR) common-mode feedforward circuit (CMFF) is used to compensate for the mirror error that is caused by the current mirror. Measurements indicate that the signal-to-noise ratio (SNR), dynamic range (DR), effective number of bits (ENOB), power consumption, and chip area are 64.1 dB, 64.4 dB, 10.36 bits, 18.82 mW, and 0.45 × 0.67 mm2 (without I/O pad), respectively, with a bandwidth of 20 kHz, an oversampling ratio (OSR) of 256, a sampling frequency of 10.24 MHz, and a supply voltage of 1.8 V.

This paper presents a resistor-compensation technique for a CMOS bandgap and current reference, which utilizes various high positive temperature coefficient (TC) resistors, a two-stage operational transconductance amplifier (OTA) and a simplified start-up circuit in the 0.35-µm CMOS process. In the proposed bandgap and current reference, numerous compensated resistors, which have a high positive temperature coefficient (TC), are added to the parasitic n-p-n and p-n-p bipolar junction transistor devices, to generate a temperature-independent voltage reference and current reference. The measurements verify a current reference of 735.6 nA, the voltage reference of 888.1 mV, and the power consumption of 91.28 µW at a supply voltage of 3.3 V. The voltage TC is 49 ppm/ in the temperature range from 0 to 100 and 12.8 ppm/ from 30 to 100. The current TC is 119.2 ppm/ at temperatures of 0 to 100. Measurement results also demonstrate a stable voltage reference at high temperature (> 30), and a constant current reference at low temperature (< 70).