Browsing by Author "Ma, Wenlong"

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28V high-linearity and rugged InGaP/GaAs power HBT
(2006)
Wang, Nanlei Larry
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Ma, Wenlong
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Xu, Sarah
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Camargo, Edmar
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Sun, Xiaopeng
This paper reports on the improvement of a previously developed InGaP/GaAs HBT for 24-28V linear power operation. The improvements achieved were: application of dynamic bias circuit which improves the ACLR under WCDMA modulation; modification of device technology improving ruggedness to sustain 10:1 VSWR at 30V collector bias under P1dB driving conditions and over 6 dB of gain compression; maintenance of lifetime and reliability simultaneously. Building blocks of HBT were strung together for higher power and good scaling of performance was achieved supporting the validity of the layout approach and the thermal design. Devices delivering P-1dB = 8W under CW conditions provided ACLR = -50 dBc at 8.5 dB back-off and 16% efficiency for WCDMA signal (PAR=8.7 dB) at 2.14 GHz. Lifetime test over 3000 hours was repeated for 28V bias and 0.05mA/um(2) current density at 315 degree C junction temperature. Therefore, the InGaP/GaAs HBT technology is mature now for the high linearity power amplification.
Averaging and cancellation effect of high-order nonlinearity of a power amplifier
(2007-12-01)
Lee, Chien-Ping
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Ma, Wenlong
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Wang, Nanlei Larry
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Nonlinear distortion of a power amplifier (PA) due to the nonlinear input-output transfer function is studied. The high-order nonlinearity or Fourier components of the output, due to the mixing of input signals, are found to be related to an average integral related to the transfer function, thus giving insight to the cancellation effect of the nonlinearity. A simple formula has been derived to relate the nth-order Fourier component of a nonlinear transfer function with a sinusoidal input to an average integral of the nth-order derivative of the transfer function. The large signal nonlinear distortion of the nth-order can therefore be regarded as a weighted average of the nth-order derivative of the transfer function. For PAs, the averaging effect gives rise to local minima in the intermodulation distortion terms during power sweep because of the cancellation of the positive part and the negative part of the derivative during averaging. We have applied the formula to InGaP heterojunction bipolar transistors PAs and are able to explain most of the observed nonlinear phenomena of the amplifiers.
Reliability study of InGaP/GaAs HBT for 28V operation
(2006)
Chau, Frank Hin-Fai
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Lin, Barry Jia-Fu
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Chen, Yan
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Kretschmar, Mark
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Lee, Chien-Ping
This paper reports the device process and reliability aspects of a high voltage InGaP/GaAs HBT technology for 28V operation. The key differences and challenges from the material and process perspectives relative to the conventional low voltage HBT technology are first described. Long-term reliability tests performed at 28V bias voltage, 5.2kA/cm(2) current density and 310 degrees C junction temperature resulted in zero device failures after over 3600 hours of stress. Wafer-level reliability tests using extreme current stress conditions were used to force transistors to degrade in short time for quick checking of transistor integrity and process reliability. Transistor lifetimes were generally higher than those in conventional low voltage HBTs at similar junction temperatures. Combining with the previously reported ruggedness and linearity performance, the high voltage InGaP/GaAs HBT is a mature technology for use in the 28V high linearity power amplification.
The safe operating area of GaAs-based heterojunction bipolar transistors
(2006-11-01)
Lee, Chien-Ping
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Chati, Frank H. E.
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Ma, Wenlong
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Wang, Nanlei Larry
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電子工程學系及電子研究所
The safe operating area (SOA) of GaAs-based heterojunction bipolar transistors has been studied considering both the self-heating effect and the breakdown effect. The Kirk effect induced breakdown (KIB) was considered to account for the decrease of the breakdown voltage at high currents. With reasonable emitter ballastors, the RIB effect was shown to be the major cause for device failure at high currents, while the thermal effect controls the low current failure. The effect of emitter resistance and base resistance on device stability was also studied. While the emitter resistance always improves the device stability by expanding the SOAs, the base resistance degrades SOAs when the KIB dominates the failure mechanism. The effect of the base resistance on SOAs was explained by its control on the flow of the avalanche current. Since the KIB effect depends on the collector structure, it was shown that a noniuniformly doped collector can effectively improve the SOAs.