Yasuhiko Kuriyama

A 40-GHz D-type flip-flop using AlGaAs/GaAs HBT's

We report master-slave D-type flip-flop (D-FF) circuit implemented with AlGaAs/GaAs HBTs. The fabricated HBTs had an f/sub T/ of 107 GHz and an f/sub max/ of 110 GHz. To maximize the speed, the logic swing and transistor size in the IC were optimized. In the D-FF, to facilitate the high-speed testing, a selector circuit was integrated on the same chip. As a result, the operation of this IC was confirmed up to 40 GHz, which is the highest speed in D-FF. >

AlGaAs/GaAs HBT receiver ICs for a 10 Gbps optical communication system

Key component ICs for an optical communication system such as an equalizing amplifier a rectifier, and a limiting amplifier were fabricated with AlGaAs/GaAs HBTs. The equalizing amplifier with an amplitude detection circuit had an 11 GHz bandwidth, 30-dB maximum voltage gain and over 30-dB controllable gain width. The rectifier could extract 10-GHz signals, and the limiting amplifier had a 36-dB voltage gain at 10 GHz and an over 20-dB dynamic range with an under 10 degrees phase-shift deviation. These optical receiver ICs have a performance sufficient for 10-Gbit/s optical communication system.<<ETX>>

Ultra-low resistance base ohmic contact with Pt/Ti/Pt/Au for high-fmax AlGaAs/GaAs heterojunction bipolar transistors

Ohmic contacts to 500-A-thick p-Al0.1Ga0.9As layer formed with a Pt/Ti/Pt/Au metal system were investigated. An extremely low contact resistivity of 4.2×10-7 Ω cm2 was obtained. The contact resistance increased with the increment of the Pt thickness, because the thicker the intermetallic layer becomes the thinner the AlGaAs layer beneath it, which leads to a higher contact resistance. The optimum Pt thickness was around 50 A. Moreover, this metal scheme was thermally stable at 350° C. A high f max of 160 GHz was obtained for AlGaAs/GaAs HBTs using Pt/Ti/Pt/Au base electrodes. A multiplexer (MUX) lC implemented with these high-f max HBTs operated properly up to 40 Gbps, the highest speed ever reported. This value was restricted by the measuring instrument capability.

DC to 40-GHz broad-band amplifiers using AlGaAs/GaAs HBT's

In this paper, we report two types of broad-band amplifiers implemented with AlGaAs/GaAs HBTs. One is a Darlington feedback amplifier and the other is a transimpedance amplifier. In the former circuit, a dc gain of 9.5 dB and a -3-dB bandwidth of 40 GHz were achieved. In the latter circuit, a transimpedance gain of 50 dB/spl Omega/ and a -3-dB bandwidth of 27 GHz were achieved. To our best knowledge, they are the highest speed in each circuit configuration. >

15 GBPS MUX/DMUX implemented with AlGaAs/GaAs HBTs

AlGaAs/GaAs HBTs (heterojunction bipolar transistors) with improved high-speed performance obtained by a self-alignment technology and a new layer design have been used to construct ultra-high-speed MUX (multiplexer) and DMUX (demultiplexer) ICs. Quantitative error-free operation of these ICs was confirmed up to 10 Gb/s. Although only a few test patterns were available, the maximum operation speeds of the MUX and the DMUX were found to be around 15 Gb/s and 19 Gb/s, respectively. These results demonstrate the promising potential of HBTs for coming ultra-high-speed digital systems.<<ETX>>

Five AlGaAs/GaAs HBT ICs for a 20 Gb/s optical repeater

The development of future ultra high bit rate optical transmission systems is now under way to meet the need for a rapid increase in transmission capacity. The capability of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is already demonstrated by a 10 Gb/s optical transmission unit This paper describes a complete 5-chip set of AlGaAs/GaAs HBT ICs for a 20Gb/s direct detection optical repeater.<<ETX>>

Ultrahigh-speed heterojunction bipolar transistor multiplexer/demultiplexer ICs

High-speed 2-b monolithic integrated multiplexer (MUX) and demultiplexer (DMUX) circuits have been developed using self-aligned AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with improved high-speed performance. Both ICs were designed using emitter-coupled logic. The 2:1 MUX was composed of a D-type flip-flop (D-FF) merging a selector gate and a T-type flip-flop (T-FF). The 1:2 DMUX consisted of two D-FFs driven at a clock of half the rate of the input data. Error-free operation with a pseudorandom pattern was confirmed up to 10 Gb/s. The rise and fall times of the output signals of both ICs were 40 and 25 ps, respectively. HBT frequency dividers were used as inputs for both ICs in order to find the maximum operation speed. Although only a few test patterns were available, the maximum operation speeds of the MUX and DMUX were found to be around 15 and 19 Gb/s, respectively. >

A Doherty power amplifier module for mobile terminals with variable linearity function

A Doherty power amplifier (PA) module for mobile terminals with variable linearity function has been developed. The linearity of the Doherty PA module is optimized according to transmission signals by a bias switching technique. The Doherty amplifier module consists of a gain amplifier and a Doherty amplifier. One GaAs HBT for a gain amplifier and two GaAs HBTs for a Doherty amplifier are integrated onto a single GaAs MMIC (1.0 mm x 1.0 mm x 0.1 mm) chip. The module achieved 26.7 (I Bin output power with less than -38 dBc adjacent channel leakage power ratio (ACLR) in W-CDMA uplink mode, and 21 dBm output power with less than 3.0% error vector magnitude (EVM) was obtained in orthogonal frequency division multiplexing (OFDM) 64-QAM mode. The developed Doherty PA module is suitable for a multi-mode terminal including various high peak-to-average power ratio (PAPR) signals such as code division multiple access (CDMA) and OFDM.

A 4-mm-square 1.9 GHz Doherty power amplifier module for mobile terminals

A miniaturized Doherty power amplifier (PA) module for mobile terminals has been developed. Two GaAs HBTs and base bias circuits for a carrier amplifier and a peak amplifier are integrated onto a single chip GaAs MMIC (1.0 mm /spl times/ 1.0 mm /spl times/ 0.1 mm), which is mounted on a ceramic substrate (4.0 mm /spl times/ 4.0 mm /spl times/ 1.5 mm, alumina, dielectric constant = 8.8). In order to miniaturize the module size, a 25-Ohm environment is introduced in the module design, and two quarter-wave-length transmission lines are embedded inside the ceramic substrate. Measurement results indicate that a power-added efficiency (PAE) of 42% at 6 dB back-off, i.e. 22 dBm output power is obtained with the newly-developed Doherty PA. In other words, an improvement of 10% in PAE is achieved compared with the theoretical PAE of a conventional class B amplifier.

An HPSK/OFDM 64-QAM Dual-Mode Doherty Power Amplifier Module for Mobile Terminals

This paper presents a miniaturized dual-mode Doherty PA module applicable for an HPSK signal and an OFDM 64-QAM signal. Dual-mode operation with identical hardware is realized by introducing a bias switching technique, which changes bias conditions of amplifiers according to transmission signals, and employing dual-mode matching circuits, which are designed based on the results of load-pull measurements using an HPSK signal and an OFDM 64-QAM signal. The Doherty PA module consists of a Doherty stage and a gain stage. Two GaAs-HBTs for a Doherty stage and one GaAs-HBT for a gain stage are integrated onto a 1 mm-square single GaAs-MMIC. In the HPSK mode, maximum output power of 26.7 dBm, power added efficiency (PAE) of 41%, and power gain of 27 dB are obtained in the condition that adjacent channel leakage power ratio (ACLR) is under -38 dBc. In the OFDM 64-QAM mode, maximum output power of 21.0dBm, PAE of 27%, and power gain of 28 dB are obtained under EVM < 3.0%. This is the first multi-mode Doherty PA module suitable for multi peak to average power ratio (PAPR) signals.