A 0.6-µW Chopper Amplifier Using a Noise-Efficient DC Servo Loop and Squeezed-Inverter Stage for Power-Efficient Biopotential Sensing

Abstract

To realize an ultra-low-power and low-noise instrumentation amplifier (IA) for neural and biopotential signal sensing, we investigate two design techniques. The first technique uses a noise-efficient DC servo loop (DSL), which has been shown to be a high noise contributor. The proposed approach offers several advantages: (i) both the electrode offset and the input offset are rejected, (ii) a large capacitor is not needed in the DSL, (iii) by removing the charge dividing effect, the input-referred noise (IRN) is reduced, (iv) the noise from the DSL is further reduced by the gain of the first stage and by the transconductance ratio, and (v) the proposed DSL allows interfacing with a squeezed-inverter (SQI) stage. The proposed technique reduces the noise from the DSL to 12.5% of the overall noise. The second technique is to optimize noise performance using an SQI stage. Because the SQI stage is biased at a saturation limit of 2VDSAT, the bias current can be increased to reduce noise while maintaining low power consumption. The challenge of handling the mismatch in the SQI stage is addressed using a shared common-mode feedback (CMFB) loop, which achieves a common-mode rejection ratio (CMRR) of 105 dB. Using the proposed technique, a capacitively-coupled chopper instrumentation amplifier (CCIA) was fabricated using a 0.18-µm CMOS process. The measured result of the CCIA shows a relatively low noise density of 88 nV/rtHz and an integrated noise of 1.5 µVrms. These results correspond to a favorable noise efficiency factor (NEF) of 5.9 and a power efficiency factor (PEF) of 11.4.

Miniaturization for wearable EEG systems: recording hardware and data processing

“…0.1Hz). Recently, on-chip pseudo-resistor or duty-cycled resistor of extremely high resistance are used for fine-tuning of very low cut-off frequency [ 61 , 62 ]. However, because of the large time-constant of the integrator, DSL has an issue of DC settling time problem.…”

Ultra-Low Power Programmable Bandwidth Capacitively-Coupled Chopper Instrumentation Amplifier Using 0.2 V Supply for Biomedical Applications

“…A negative voltage V NEG generated by the negative bias generator (see Figure 3) is used to bias the PM input transistor via a pseudo-resistor R P1 , 2 . The gate voltage of the transistor NM is controlled by a common CMFB loop [10] driven by a high voltage source V DD,H = 0.8-V to maintain the common output voltage of SQI at V DD,L /2. Capacitors C S1,2 are used for AC coupling.…”

“…However, the IA has two important noise sources that must be taken into account, flicker noise (1/f ) and thermal noise [8]. The chopper stabilization technique is commonly used on IA [9,10] to mitigate 1/f noise by up-modulating this noise at low frequencies beyond the spectrum of IA, while leaving thermal noise unresolved. For example, although the designs in [11,12] consume only 2 µW and 1.89 µW, thermal noise remains a concern with values of 100 and 240 nV/Hz, 2 of 12 respectively.…”

Design a low power, 100dB operational amplifier using CMOS technology

“…Today's system-on-chip (SOC) applications required the integration of both analog and digital components to address non-functional constraints [1][2][3][4][5][6][7][8]. The best-picked topology can aid with the appropriate design of analog and digital circuits.…”