Masatomo Hasegawa

A 3.5 W HBT MMIC power amplifier module for mobile communications

A 900 MHz-band GaAs/GaAlAs HBT MMIC power amplifier module has been developed for mobile communications by using a novel assembly technique called BHS and an AlN package as the MMIC chip carrier. The power module gave a peak output power of 3.7 W and a power-added efficiency of 54.5% with a +6 V single supply voltage.<<ETX>>

Bump heat sink technology - A novel assembly technology suitable for power HBTs

A novel assembly technique, bump heat sink (BHS), suitable for compound semiconductor power HBTs is proposed and demonstrated. In this technique, the heat generated in the transistor junction is effectively conducted away through a gold bump which is located on the top of each transistor unit. Using this technique, power transistors are demonstrated with power added efficiencies /spl eta//sub add/ of 74%, 66% and 61% for 5.0 W, 8.0 W and 10.0 W output CW, respectively, at 0.9 GHz with V/sub cc/=6 V. A three-stage HBT MMIC power amplifier for GSM class 4 is also demonstrated with /spl eta//sub add/ >55% at V/sub cc/=4 V CW operation.<<ETX>>

A High-Power Low-Distortion GaAs HBT Power Amplifier for Mobile Terminals Used in Broadband Wireless Applications

This paper describes technologies of miniaturized high-power low-distortion GaAs HBT power amplifiers with a low-voltage operation for mobile terminals used in 5-6 GHz broadband wireless applications. In conjunction with diode-based linearizing techniques, wideband matching network techniques including trap circuits for second harmonics allow us to obtain a compact broadband power amplifier module with harmonic filtering, achieving the high linear output power at a low supply voltage together with the low distortion and the low second-harmonic spurious outputs in a wide frequency range. The fabricated power amplifier exhibited linear output power levels of 21 and 22 dBm at EVM values of 2.0 and 3.0%, respectively, measured with 54 Mb/s 64-QAM-OFDM signals at a supply voltage of 3.3 V in a frequency range of 5-6 GHz. Second harmonic spurious outputs below -35 dBc were also attained.

A 5 GHz high efficiency and low distortion InGaP/GaAs HBT power amplifier MMIC

An InGaP/GaAs two-stage HBT power amplifier for 5 GHz Wireless-LAN applications was developed. By using a self-aligned base contact formation process and an external base region side etching process, a high gain HBT was realized. A small-sized via hole fabrication process was developed. The gain of multi-finger HBT was improved by locating via holes between each finger. Linearity was also improved by developing a new variable negative feedback circuit. A power amplifier MMIC utilizing this technology was fabricated, and 19.7 dBm output power, 22 dB gain, 22.5% power-added-efficiency (PAE), 5.0% error vector magnitude (EVM) were obtained at 54 Mbps transmission under a supply voltage of 3.3 V. These state of the art data represent the highest PAE reported for a the power amplifier MMIC in the 5 GHz Wireless-LAN application.

Analytical model for electrical and thermal transients of self-heating semiconductor devices

Transients of self-heating semiconductor devices are theoretically investigated based on a feedback circuit model, which is composed of three sub-circuits describing the isothermal electrical characteristics, thermal impedance, and temperature dependence of the electrical characteristics of the devices, respectively. Analytical expressions of the frequency and transient responses have been derived for both the electrical and thermal characteristics of self-heating devices, yielding accurate methods to extract the thermal time constant in both the time and frequency domains. The model is verified by the transient electrical-response measurement of a GaInP/GaAs heterojunction bipolar transistor.

Enhanced linearity and efficiency of HBT power amplifiers for 5-GHz wireless-LANs

This paper describes two advanced techniques to enhance linearity and efficiency in HBT power amplifiers (PA) for 5-GHz wireless-LANs (W-LANs). The diode-based linearizing circuit successfully compensates the gain expansion of PAs operating at a low quiescent current. The output matching circuit consisting of on-chip MIM capacitors and bond wires effectively reduces the loss of the circuit as well as allowing the miniaturization of the PA module. The PA MMIC fabricated incorporating these techniques achieved an improvement in linear output power and PAE of 2.4 dBm and 4.8%, respectively, compared to our previous PA with the same device dimensions, and exhibited an output power of 22.1 dBm and a PAE of 27.3% at an EVM of 5%, measured with 54Mbps 64-QAM-OFDM signals at 5.25 GHz.

A High Efficiency InGaP/GaAs HBT Power Amplifier MMIC for the 5GHz Wireless-LAN Application

An InGaP/GaAs two-stage HBT linear power amplifier MMIC for the 5GHz Wireless-LAN Application was developed. By using a novel linearizer and a small-size via-hole technology, the power amplifier showed high output power (19dBm) with high power-added-efficiency (PAE : 18.5%), sufficient gain (21.0dB) and high linearity (4.78% error vector magnitude : EVM) at supply voltage 3.3V. It is the highest PAE in the power amplifier MMIC for the 5GHz Wireless-LAN application ever reported.

High-performance InGaP power HBT technologies for wireless applications

We review the technological features of our InGaP power HBTs for 5GHz wireless application. The features include self-aligned base-contact and base-mesa formation process, small-sized via holes located between multi-finger transistors, and bias and feedback circuits for the reduction of distortion. These technologies improve both gain and linearity, producing higher power added efficiency (PAE) in power amplifiers.

Compensation of self-heating effect in DC and pulse characteristics of HBTs

A simple technique to compensate the self-heating effect in DC and pulse characteristics of HBTs is proposed and demonstrated. Due to the cancellation of the positive and negative thermal-electric feedback inside HBTs, the compensation is achieved by inserting a specified resistance in the base bias circuit. An analytical expression specifying the resistance is also presented.

Analytical expressions of transient thermal response of self-heating semiconductor devices

Analytical expressions of the transient thermal response of self-heating devices have been derived based on a feedback amplifier circuit model yielding accurate methods to extract the thermal time constant in both the time and frequency domains. The transient thermal responses of GaInP/GaAs HBT were measured and explained using the expressions derived.