There is a need among scientists and clinicians for low-noise low-power biosignal amplifiers capable of amplifying signals in the millihertz-to-kilohertz range while rejecting large dc offsets generated at the electrode-tissue interface. The advent of fully implantable multielectrode arrays has created the need for fully integrated micropower amplifiers. We designed and tested a novel bioamplifier that uses a MOS-bipolar pseudoresistor element to amplify low-frequency signals down to the millihertz range while rejecting large dc offsets. We derive the theoretical noise-power tradeoff limit - the noise efficiency factor - for this amplifier and demonstrate that our VLSI implementation approaches this limit by selectively operating MOS transistors in either weak or strong inversion. The resulting amplifier, built in a standard 1.5-/spl mu/m CMOS process, passes signals from 0.025Hz to 7.2 kHz with an input-referred noise of 2.2 /spl mu/Vrms and a power dissipation of 80 /spl mu/W while consuming 0.16 mm/sup 2/ of chip area. Our design technique was also used to develop an electroencephalogram amplifier having a bandwidth of 30 Hz and a power dissipation of 0.9 /spl mu/W while maintaining a similar noise-power tradeoff.

A low-power low-noise CMOS amplifier for neural recording applications

The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

/pdf/statistical-theory-of-communication-4wy4yg9ato.pdf

Statistical Theory of Communication

Using sigma-delta A/D methods, high resolution can be obtained for only low to medium signal bandwidths. This article describes conventional A/D conversion, as well as its performance modeling. We then look at the technique of oversampling, which can be used to improve the resolution of classical A/D methods. We discuss how sigma-delta converters use the technique of noise shaping in addition to oversampling to allow high resolution conversion of relatively low bandwidth signals. We examine the use of sigma-delta converters to convert narrowband bandpass signals with high resolution. Several parallel sigma-delta converters, which offer the potential of extending high resolution conversion to signals with higher bandwidths, are also described.

An overview of sigma-delta converters

Introduction. UWB Channel Models. Modulation Schemes. Receiver Structures. Integrated Circuit Topologies. UWB Antennas. Medium Access Control. Positioning.

UWB theory and applications

https://www.eecg.toronto.edu/~johns/ece1371/slides/13_nyquist_ad.pdf

Nyquist-Rate A/D Converters

In this paper, an open source inertial sensor network is presented. The network has multiple sensor nodes connecting to a consumer electronic device with Bluetooth Smart. Each sensor node contains the following components: (a) an inertial sensor measuring acceleration, angular velocity, and magnetic field with good accuracy; (b) a microcontroller with capacity to handle real-time floating number calculations; (c) a Bluetooth Smart module broadcasting the data with low power consumption. The sensor nodes are designed to be small, allowing the users to wear them conveniently. For demonstration, a basic Personal Navigation System is developed using 4 of these sensor nodes and an Android smartphone. The experiments show that the sensor nodes could output accurate results with small noises when at rest or in slow motion. The example Personal Navigation System could measure total distance walked by a pedestrian with less than 10% error.

/pdf/an-open-source-inertial-sensor-network-with-bluetooth-smart-1dev4066ub.pdf

An open source inertial sensor network with Bluetooth Smart

In this chapter, to improve the reliability and cost of signal processing electronics, entire systems must be integrated on to a single chip. In many applications, an all-digital or all-analogue system is impossible because both analogue and digital external interfaces are required. So we must assume that both analogue and digital circuits will have to coexist on the same IC. The advance of digital process technologies will enable faster digital signal processing with a smaller integrated circuit area and lower power consumption. At the same time it will become increasingly difficult to implement accurate and linear analogue circuits. Therefore, analogue adaptive filters are likely to continue to be targeted at applications where they can simplify or reduce the analogue circuitry required elsewhere on the chip.

Analogue adaptive filters

Incremental ADCs can operate at lower oversampling ratios than DeltaSigma modulators, resulting in higher input signal bandwidths. In this paper it is shown that time-interleaving can further increase the input signal bandwidth in incremental ADCs to the point that the oversampling ratio is equal to the time-interleaving factor, resulting in no decrease in the allowable input signal bandwidth due to oversampling. This paper investigates some of the advantages and challenges that time-interleaved incremental ADCs offer, and presents an example where a time-interleaved by 4 incremental ADC with an oversampling ratio of 4 can attain a resolution of 12 bits.

Time-interleaved incremental data converters with low oversampling ratios

We present two approaches for performance-enhancement of compensation methods in delta-sigma modulation. A robust modulator architecture featuring variable-structure control is also proposed. Simulations are provided to demonstrate the effectiveness of these techniques in improving resolution and dynamic range.

David A. Johns

Papers

Nyquist-Rate A/D Converters

An open source inertial sensor network with Bluetooth Smart

Analogue adaptive filters

Time-interleaved incremental data converters with low oversampling ratios

Variable-structure delta-sigma modulators with resolution enhancement strategies