Quoc-Hoang Duong

A 95-dB linear low-power variable gain amplifier

An all-CMOS variable gain amplifier (VGA) that adopts a new approximated exponential equation is presented. The proposed VGA is characterized by a wide range of gain variation, temperature-independence gain characteristic, low-power consumption, small chip size, and controllable dynamic gain range. The two-stage VGA is fabricated in 0.18-mum CMOS technology and shows the maximum gain variation of more than 95 dB and a 90-dB linear range with linearity error of less than plusmn 1 dB. The range of gain variation can be controlled from 68 to 95 dB. The P1dB varies from - 48 to - 17 dBm, and the 3-dB bandwidth is from 32 MHz (at maximum gain of 43 dB) to 1.05 GHz (at minimum gain of - 52 dB). The VGA dissipates less than 3.6 mA from 1.8-V supply while occupying 0.4 mm2 of chip area excluding bondpads

CMOS exponential current-to-voltage circuit based on newly proposed approximation method

This paper proposed a low-voltage and low-power current-to-voltage converter with controllable transconductance. The proposed circuit uses a newly proposed approximation function to increase the dB-linear output range. In a 0.25 /spl mu/m CMOS process, the simulations show a 58 dB output voltage range and a 46 dB with the linearity error less than /spl plusmn/0.5 dB. The average power dissipation is less than 0.8 mW at 1.5 V supply voltage. The proposed circuit can be used for the design of an extremely low-voltage and low-power variable gain amplifier (VGA) and automatic gain control (AGC).

An all CMOS 84dB-linear low-power variable gain amplifier

A new exponential approximation function is implemented into a variable gain amplifier (VGA). The newly proposed VGA topology provides low-power, small chip size, and wide control gain range. The VGA is fabricated in 0.18/spl mu/m CMOS technology and measurements show a gain variation of more than 84dB in two cascaded stages, and 80dB-linear range with a linearity error of less than /spl plusmn/1dB. The PldB varies from -42dBm to -22dBm. The power dissipation is less than 3.6mA from 1.8V supply. The chip excluding bondpads occupies 0.4mm/sup 2/.

Low-voltage low-power high dB-Linear CMOS exponential function generator using highly-linear V-I converter

A CMOS voltage-to-current converter with exponential characteristic is presented in this paper. The concept of Taylor series expansion is used for realizing the exponential characteristic. The proposed exponential V-I converter is composed of a current-to-current squarer and a linear V-I converter with the use of linearization technique. Based on a 0.25 mm CMOS process, simulations show a 23 dB of linear-output current range and the linearity within 20 dB with error less than ± 0.5dB is achieved. The total power consumption is below 0.2 mW with 1.25 V supply voltage. The proposed circuit can be used for the design of an extremely low-voltage low-power variable gain amplifier (VGA).

All CMOS current-mode exponential function generator

This paper proposed an ultra low-voltage low-power all CMOS current-mode exponential function circuit. The design of the circuit is based on Taylor series expansion for realizing the exponential characteristic and composed of MOS transistors operating in the saturation region. The advantages of the circuit are that its input range can he tuned by adjusting the biased current and its output current presents a very low temperature coefficient. The simulations, based on a 0.25 μm CMOS process, show a 20 dB linear output current range and a 15 dB-linear range with the linearity error less than ± 0.5 dB at 1.2SV supply voltage. The proposed circuit could he used for the design of an extremely low-voltage low-power automatic gain control (AGC) and variable gain amplifier (VGA).

A 35 dB-linear exponential function generator for VGA and AGC applications

In this paper, a new current-mode based exponential function generator with high dB-linear range is developed. The exponential function is based on Taylors concept. The proposed circuit is composed of current-to-current squarers, current multipliers, and a linear V-I converter with linearization technique. Based on a 0.25 μm CMOS process, the simulations show a 35 dB-linear output current range with the linearity error less than ± 0.5 dB. The power dissipation is less than 0.3 mW at 1.25 V supply voltage.

An all CMOS 743 MHz variable gain amplifier for UWB systems

A newly proposed variable gain amplifier (VGA) that offers wide bandwidth and gain variation characteristics is described for ultra wideband system applications. The proposed VGA combines a cascade-input stage and bandwidth-extension loads to obtain a wide bandwidth. The VGA is simulated in 0.13 mum CMOS technology and simulations show a gain variation range of 54 dB in a single-stage VGA and a minimum 1-dB bandwidth of 743 MHz at the maximum gain of 20 dB. The 1-dB bandwidth improvement of 58% compared to conventional VGAs at the same supply current is obtained. In addition, the newly proposed control stage results in a compact VGA, which leads to low power consumption. The VGA dissipates an average supply current of 4.5 mA from 1.8 V supply voltage

A low power CMOS transceiver for 915 MHz-band IEEE 802.15.4b standard

This paper presents a low power and low cost transceiver for 915 MHz-band IEEE 802.15.4 b standard. Low power and low cost design are considered by optimizing transceiver architecture and circuit topology. The proposed transceiver shares analog baseband for both receiver and transmitter saving a silicon area. The transceiver consumes 11.5 mA and 22.5 mA for receive and transmit mode from 1.8 V supply including 5 mA of VCO and frequency divider currents. The proposed transceiver is implemented in a 0.18 mum CMOS process and occupies 10 mm of silicon area.

A low-voltage low-power high dB-linear and all CMOS exponential V-I conversion circuit

A very compact, all CMOS, exponential V-I conversion circuit is proposed for low-voltage and low-power applications. The exponential characteristic is based on the Taylor concept. A new technique to improve the dB-linear output current range of the V-I circuit has been introduced. Based on a 0.18 /spl mu/m CMOS process, the measured results show 44 dB of output current range with a very low current consumption of less than 0.18 mA from a 1.2 V supply voltage. The chip size, excluding bond-pads, is 170/spl times/90 /spl mu/m. The proposed circuit can be used for the design of low-voltage, low-power analog and mixed-mode circuits such as variable gain amplifiers (VGA), automatic gain control (AGC), etc.

dB-linear V-I converter using composite NMOS transistor

A new CMOS exponential V-I converter (EVIC), based on Taylors concept and using NMOS transistor, is presented in this paper. The proposed-modified Taylor series expansion is used to extend the dB-linear output current range. In a 0.25 /spl mu/m CMOS process, the simulations show more than 22 dB output current range and 17 dB linear range with the linearity error less than /spl plusmn/0.5 dB. The power dissipation is less than 0.3 mW with /spl plusmn/1.5 V supply voltage. The proposed EVIC can be used for the design of an extremely low-voltage and low-power variable gain amplifier (VGA) and automatic gain control (AGC).