Quantifying Biomedical Amplifier Efficiency: The noise efficiency factor

There has been a long-standing interest in controlling and instrumenting the human body. Whether to restore lost function with neural prosthetics, monitor blood glucose levels, or augment human capabilities, there are countless opportunities for sensors inside ( e.g., ingestible, injectable, and implantable) and outside ( e.g., wearable) the...

The Zoom ADC: An Evolving Architecture

Zoom ADCs combine a coarse SAR ADC with a fine delta-sigma modulator (?SM) to efficiently obtain high energy efficiency and high dynamic range. This makes them well suited for use in various instrumentation and audio applications. However, zoom ADCs also have drawbacks. The use of over-ranging in their fine modulators may limit SNDR, large...

An Auto-Zero-Stabilized Voltage Buffer With a Quiet Chopping Scheme and Constant Sub-pA Input Current

This article describes an auto-zero stabilized voltage buffer that achieves low offset and low noise with sub-pA input current. A high gain stabilization loop is used to periodically cancel the buffer’s offset. The loop itself is periodically disconnected from the buffer and auto-zeroed, during which its bandwidth is reduced to reduce the...

A MEMS Coriolis-Based Mass-Flow-to-Digital Converter for Low Flow Rate Sensing

This article presents a microelectromechanical system (MEMS) Coriolis-based mass-flow-to-digital converter (Φ DC) that can be used with both liquids and gases. It consists of a micromachined Coriolis mass flow sensor and a CMOS interface circuit that drives it into oscillation and digitizes the resulting mass flow information. A phase-locked...

A 590 μw, 106.6 dB SNDR, 24 kHz BW Continuous-Time Zoom ADC with a Noise-Shaping 4-bit SAR ADC

This paper presents a continuous-Time zoom ADC for audio applications. It combines a 4-bit noise-shaping coarse SAR ADC and a fine delta-sigma modulator with a tail-resistor linearized OTA for improved linearity, energy efficiency, and handling of out-of-band interferers compared to previous designs. In 160 nm CMOS, the prototype chip...

A 121.4-dB DR Capacitively Coupled Chopper Class-D Audio Amplifier

This article presents a class-D amplifier (CDA) with high dynamic range (DR). To eliminate the typically dominant noise contribution of a resistive feedback network, the input and feedback signals are chopped and applied to a capacitive feedback network. However, this leads to high-voltage (HV) transients at the input of the loop filter,...

A Low-Field Portable Nuclear Magnetic Resonance (NMR) Microfluidic Flowmeter

This paper presents a portable and contactless microfluidic flowmeter based on the Nuclear Magnetic Resonance (NMR) principle, which can measure flow rates up to 2.7 ml/min with \pm 16\ lmin (±0.6% full-scale) error. It consists of a millimeter-size RF coil wound around a microfluidic channel, custom readout electronics and a 0.5 T permanent...

An Auto-Zero Stabilized Voltage Buffer with a Quiet Chopping Scheme and Constant Input Current

The readout of high-impedance sensors and sampled voltage references [1] requires amplifiers that can achieve both low offset and low input current. Recently, it has been shown that this unique combination can be achieved by an auto-zero (AZ) stabilized buffer [2]. However, its low-frequency noise density is surd 5 times higher than the...

A 0.12mm² Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C

Resistor-based temperature sensors can achieve much higher resolution and energy efficiency than conventional BJT-based sensors [1], but they typically occupy more area (> 0.25 mm ² ) and have lower operating temperatures (le 125 {circ} {C}) [2]-[4]. This work describes a 0.12mm ² resistor-based sensor that uses a...

A Wheatstone Bridge Temperature Sensor with a Resolution FoM of 20fJ.K ²

Temperature sensors intended for embedded applications should be both energy-and area-efficient. The combination of Wheatstone-bridge (WhB) sensors and continuous-time ADCs has proven to be highly energy efficient [1], [2]. However, their area (> 0.25 mm{2}) is still larger than that of comparable BJT-based sensors [3], [4]. This paper...

A 280μW dynamic-zoom ADC with 120dB DR and 118dB SNDR in 1kHz BW

Micro-power ADCs with high linearity and dynamic range (DR) are required in several applications, such as smart sensors, biomedical imaging, and portable instrumentation. Since the signals of interest are then often small (tens of μν) and slow (<1kHz BW), such ADCs should also exhibit low offset and flicker noise. Noise-shaping SAR [1] and...

A 4.5 nV/√Hz Capacitively Coupled Continuous-Time Sigma-Delta Modulator with an Energy-Efficient Chopping Scheme

When chopping is applied to a continuous-time sigmadelta modulator (CTΣΔM), quantization noise fold-back often occurs, leading to increased in-band noise. This can be prevented by employing a return-to-zero (RZ) digital-to-analog converter (RZ DAC) in the modulator's feedback path and arranging the chopping transitions to coincide with its RZ...

A Resistor-Based Temperature Sensor with a 0.13pJ·K2 Resolution FOM

Temperature sensors are often used for the temperature compensation of frequency references [1-5]. High resolution and energy efficiency are then critical requirements, the former to minimize jitter and the latter to minimize power dissipation in a given conversion time. A MEMS-resonator-based sensor meets both criteria [1], but requires two...

Analysis and Design of VCO-Based Phase-Domain ΣΔ Modulators

VCO-based phase-domain ΣΔ modulators employ the combination of a voltage-controlled-oscillator (VCO) and an up/down counter to replace the analog loop filter used in conventional ΣΔ modulators. Thanks to this highly digital architecture, they can be quite compact, and are expected to shrink even further with CMOS scaling. This paper describes...

A 20-bit ±40-mV Range Read-Out IC With 50-nV Offset and 0.04% Gain Error for Bridge Transducers

This paper presents a 20-b read-out IC with ±40-mV full-scale range that is intended for use with bridge transducers. It consists of a current-feedback instrumentation amplifier (CFIA) followed by a switched-capacitor incremental ΔΣ ADC. The CFIA's offset and 1/ <i>f</i> noise are mitigated by chopping, while its gain accuracy and gain drift are...

A chopper current-feedback instrumentation amplifier with a 1 mHz 1/f noise corner and an AC-coupled ripple reduction loop

This paper presents a chopper instrumentation amplifier for interfacing precision thermistor bridges. For high CMRR and DC gain, the amplifier employs a three-stage current-feedback topology with nested-Miller compensation. By chopping both the input and intermediate stages of the amplifier, a 1 mHz 1/f noise corner was achieved at an input...