Yaohui Kong

Bio: Yaohui Kong is an academic researcher from Tsinghua University. The author has contributed to research in topics: Low voltage & Total harmonic distortion. The author has an hindex of 2, co-authored 3 publications receiving 22 citations. Previous affiliations of Yaohui Kong include Chinese Ministry of Public Security.

An Ultra Low Output Resistance and Wide Swing Voltage Follower

Abstract: A new voltage follower with ultra low output resistance and wide swing as features is proposed. A comparison of output resistance and signal swing among some voltage followers is made. The new voltage follower is developed in 0.18 um CMOS process and 1.5 V supply voltage. The THD of output voltage can still maintain around 0.1% when 1 MHz 0.8 V input voltage swing is applied. Simulation results show that the newly introduced voltage follower has optimal characteristics.

A highly linear low voltage CMOS triode transconductor

Abstract: The paper presents a highly linear CMOS triode transconductor with a wide tuning capability for low voltage and low power applications. The use of a novel feedback loop regulating the drain voltage of input transistor in triode region achieves a highly linear voltage to current conversion. This design uses UMC 0.18 um CMOS process. Simulation result shows the proposed transconductor, operated in 1.2 V supply voltage, has less than 0.1% total harmonic distortions (THD) for 1 MHz 0.8 Vp-p differential input. The power consumption is 203 uW, when 0.55 V control voltage is applied.

KHN-equivalent voltage-mode filters using universal voltage conveyors

Abstract: The analog circuit design is very often focused on the design of frequency filters employing different types of active elements. In this paper we present the universal voltage conveyor that is used for the design of the KHN-equivalent filters working in the voltage-mode. Auxiliary voltage inputs of the active elements are used to reduce the number of floating admittances in the structure. Both proposed structures are easily cascadable since the input and output impedances are in theory infinitely high and zero, respectively. The behavior of the filters has been verified through PSpice simulations and furthermore by experimental measurements.

Super source follower output impedance enhancement

Abstract: A source follower circuit is disclosed with an added amplifier that extends the low input voltage linear range while providing a lower output impedance. The drain of the source follower MOSFET is coupled to a gain stage that drives a second MOSFET (or other type transistor) with its drain coupled to the follower output. High impedance current sources bias the circuitry, and the difference amplifier has a reference voltage at one input. The difference amplifier with the reference voltage provides a feedback mechanism that maintain adequate drain to source voltage across the follower MOSFET to enhance the low input voltage linearity along with reducing the follower output resistance.

A 0.9 V Supply OTA in 0.18 μm CMOS Technology and Its Application in Realizing a Tunable Low-Pass Gm-C Filter for Wireless Sensor Networks

Abstract: A low voltage low power operational transconductance amplifier (OTA) based on a bulk driven cell and its application to implement a tunable Gm-C filter is presented. The linearity of the OTA is improved by attenuation and source degeneration techniques. The attenuation technique is implemented by bulk driven cell which is used for low supply voltage circuits. The OTA is designed to operate with a 0.9 V supply voltage and consumes 58.8 μW power. A 600 mVppd sine wave input signal at 1 MHz frequency shows total harmonic distortion (THD) better than -40 dB over the tuning range of the transconductance. The OTA has been used to realize a tunable Gm-C low-pass filter with gain tuning from 5 dB to 21 dB with 4 dB gain steps, which results in power consumptions of 411.6 to 646.8 μW. This low voltage filter can operate as channel select filter and variable gain amplifier (VGA) for wireless sensor network (WSN) applications. The proposed OTA and filter have been simulated in 0.18 μm CMOS technology. Corner case and temperature simulation results are also included to forecast process and temperature variation affects after fabrication.

A 0.8‐V supply bulk‐driven operational transconductance amplifier and Gm‐C filter in 0.18 µm CMOS process

Abstract: Summary A low voltage bulk-driven operational transconductance amplifier (OTA) and its application to implement a tunable Gm-C filter are presented. The linearity of the proposed OTA is achieved by nonlinear terms cancelation technique, using two paralleled differential topologies with opposite signs in the third-order harmonic distortion term of the differential output current. The proposed OTA uses 0.8 V supply voltage and consumes 31.2 μW. The proposed OTA shows a total harmonic distortion of better than −40 dB over the tuning range of the transconductance, by applying 800 mVppd sine wave input signal with 1 MHz frequency. The OTA has been used to implement a third-order low-pass Gm-C filter, which can be used for wireless sensor network applications. The filter can operate as the channel select filter and variable gain amplifier, simultaneously. The gain of the filter can be tuned from −1 to 23 dB, which results in power consumptions of 187.2 to 450.6 μW, respectively. The proposed OTA and filter have been simulated in a 0.18 µm CMOS technology. Simulations of process corners and temperature variations are also included in the paper. Copyright © 2014 John Wiley & Sons, Ltd.