Circuit Techniques in GaN Technology for High-Temperature Environments

As a wide bandgap semiconductor, Gallium Nitride (GaN) device proves itself as a suitable candidate to implement high temperature (HT) integrated circuits. GaN500 is a technology available from the National Research Council of Canada to serve RF applications. However, this technology has the potential to boost HT electronics to higher ranges of operating temperatures and to higher levels of integration. This paper summarizes the outcome of five years of research investigating the implementation of GaN500-based circuits to support HT applications such as aerospace missions and deep earth drilling. More than 15 integrated circuits were implemented and tested. We performed the HT characterization of passive elements integrated in GaN500 including resistors, capacitors, and inductors up to 600 °C. Moreover, we developed for the first time several digital circuits based on GaN500 technology, including logic gates (NOT, NAND, NOR), ring oscillators, D Flip-Flop, Delay circuits, and voltage reference circuits. The tested circuits are fabricated on a 4 mm × 4 mm chip to validate their functionality over a wide range of temperatures. The logic gates show functionality at HT over 400 °C, while the voltage reference circuits remain stable up to 550 °C.

Fundamental limits of high-efficiency silicon and compound semiconductor power amplifiers in 100-300 GHz bands

This paper reviews the requirements for future digital arrays in terms of power amplifier requirements for output power and efficiency and the device technologies that will realize future energy-efficient communication and sensing electronics for the upper millimeter-wave bands (100-300 GHz). Fundamental device technologies are reviewed to compare the needs for compound semiconductors and silicon processes. Power amplifier circuit design above 100 GHz is reviewed based on load line and matching element losses. We present recently presented class-A and class-B PAs based on a InP HBT process that have demonstrated record efficiency and power around 140 GHz while discussing circuit techniques that can be applied in a variety of integrated circuits.

A Soft-Error-Tolerant SAR ADC with Dual-Capacitor Sample-and-Hold Control for Sensor Systems

For a reliable and stable sensor system, it is essential to precisely measure various sensor signals, such as electromagnetic field, pressure, and temperature. The measured analog signal is converted into digital bits through the sensor readout system. However, in extreme radiation environments, such as in space, during flights, and in nuclear fusion reactors, the performance of the analog-to-digital converter (ADC) constituting the sensor readout system can be degraded due to soft errors caused by radiation effects, leading to system malfunction. This paper proposes a soft-error-tolerant successive-approximation-register (SAR) ADC using dual-capacitor sample-and-hold (S/H) control, which has robust characteristics against total ionizing dose (TID) and single event effects (SEE). The proposed ADC was fabricated using 65-nm CMOS process, and its soft-error-tolerant performance was measured in radiation environments. Additionally, the proposed circuit techniques were verified by utilizing a radiation simulator CAD tool.

A CMOS Optoelectronic Receiver IC with an On-Chip Avalanche Photodiode for Home-Monitoring LiDAR Sensors

This paper presents an optoelectronic receiver (Rx) IC with an on-chip avalanche photodiode (APD) realized in a 0.18-mm CMOS process for the applications of home-monitoring light detection and ranging (LiDAR) sensors, where the on-chip CMOS P+/N-well APD was implemented to avoid the unwanted signal distortion from bondwires and electro-static discharge (ESD) protection diodes. Various circuit techniques are exploited in this work, such as the feedforward transimpedance amplifier for high gain, and a limiting amplifier with negative impedance compensation for wide bandwidth. Measured results demonstrate 93.4-dBW transimpedance gain, 790-MHz bandwidth, 12-pA/√Hz noise current spectral density, 6.74-mApp minimum detectable signal that corresponds to the maximum detection range of 10 m, and 56.5-mW power dissipation from a 1.8-V supply. This optoelectronic Rx IC provides a potential for a low-cost low-power solution in the applications of home-monitoring LiDAR sensors.

Accuracy and Physical Characterization of Approximate Arithmetic Circuits

With the end of Dennard's scale, designers have been looking for new alternatives and approximate computing (AC) has managed to attract the attention of researchers, by offering techniques ranging from the application level to the circuit level. When applying approximate circuit techniques in hardware design, the program user may speed up the application while a designer may save area and power dissipation at the cost of less accuracy on the operations results. This paper discusses the compromise between accuracy versus physical efficiency by presenting a set of experiments and results of tailor-made approximate arithmetic circuits on Field-Programmable Gate Array (FPGA) platforms. Our results reveal that an approximate circuit with accuracy control could not be useful if the goal is to save circuit area or even power dissipation. Even for circuits that seem to have power efficiency, we should care about the size and prototyping platform where the hardware will be used.