Xiaopeng Sun

28V High-Linearity and Rugged InGaP/GaAs Power HBT

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 P1dB equiv 8W under CW conditions provided ACLR equiv -50 dBc at 8.5 dB back-off and 16% efficiency for WCDMA signal (PARequiv8.7 dB) at 2.14 GHz. Lifetime test over 3000 hours was repeated for 28V bias and 0.05mA/mum2 current density at 315 degree C junction temperature. Therefore, the InGaP/GaAs HBT technology is mature now for the high linearity power amplification

High efficiency 28V class AB InGaP/GaAs HBT MMIC amplifier with integrated bias circuit

InGaP/GaAs HBTs have demonstrated excellent lifetime and linearity performance for 3 to 10 V operation. This is very attractive for infrastructure applications. However, the low voltage is a drawback in this application where 28 V is a common voltage used. In this effort, a high voltage InGaP/GaAs HBT is developed for 28 V operation. The safe operation area is carefully designed, allowing the device to function in class A mode. A thermal resistance of 30/spl deg/C/W for a 1 W HBT design is measured using the V/sub be/ method. 4 W CW power with 71% efficiency is measured from this 1 W design, with a junction temperature rise of 49/spl deg/C. The integrated temperature compensated bias circuit provides <9% quiescent current change over base plate temperatures from -40 to +85/spl deg/C. Two tone and CDMA2000 linearity is also characterized. Initial WLR (wafer level reliability) results indicate that it has a similar lifetime to the standard InGaP/GaAs HBT.

Linearity improvement of multi-Watts 24-28 V InGaP/GaAs HBT by low frequency low source impedance matching

InGaP/GaAs HBT running at 24-28 V operation voltage has demonstrated over 20 W output power in the standard MMIC format with efficiency over 60%. On-chip power combining of multiple HBT building-blocks successfully delivered the power transistor with multi-tens watt output power without any undesired spur. Two-tone linearity and other modulation signal were used to characterize the linearity of the HBT power transistor. By properly matching the HBT at the RF frequency, as well as the low frequency source impedance, linearity is clearly improved. WCDMA signal with ACLR1=-45 dBc is achieved with only 8 dB backoff, as compared with the WCDMA test method 1 of 9.8 dB peak-to-average ratio; the efficiency reaches 20%. This effort clearly demonstrated the potential of InGaP/GaAs HBT in the high power, high voltage operation.

Reliability Study of InGaP/GaAs HBT for 28V Operation

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/cm2 current density and 310degC 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

High linearity 40 watt, 28V InGaP/GaAs HBT

This paper reports on a 40W high linearity InGaP/ GaAs 28V HBT. It uses a high breakdown voltage, high ruggedness HBT process developed by WJ. The device employs a dynamic bias circuit to improve ACLR under WCDMA modulation conditions. The P-1dB of the device reaches 46dBm (40W), with a gain around 14.5dB. With WCDMA one carrier modulation (PAR=8.5dBc), the device achieves an ACLR of −50dBC and an efficiency of 19.5% at an output power of 37.5dBm (5.6W) at 920–960MHz frequency band. Without the help of a DPD, the performance of this device will make it an excellent choice for base station and repeater applications.

1.5–2.7 GHz ultra low noise bypass LNA

Bypass low-noise amplifier (LNA) can be used in the base station receiver to improve the dynamic range. It is difficult to achieve both ultra low noise at LNA mode and maintain good linearity at bypass mode simultaneously. In this work, we present the best performance bypass LNA with 0.5 dB of noise figure (NF), 20 dB of gain at 1.95 GHz and high OIP3 of 35 dBm for both LNA and bypass mode. Fabricated in 0.25um GaAs E/D pHEMT process, the LNA is based on enhancement mode pHEMT cascode topology and the switches are designed with the depletion mode pHEMT.

A scalable high power nonlinear HBT model for a 28V HVHBT

A scalable nonlinear HBT model for a Building Block (1BB) of 28V InGaP/GaAs HBT is presented. It is based on the AgilentHBT (AHBT) model. The building block consists of 32 finger HBTs, an input pre-matching circuit and a transistor used as an emitter follower in the related bias circuit. The P1dB of 1BB is 32.5dBm. The model can account not only for DC, thermal, junction capacitances, S-parameters but also RF power, gain, IM3, operation current and collector efficiency. A good match between simulation and measurement has been achieved. By using a multiplicity parameter the model can accurately predict the DC and nonlinear RF performance of two Building Blocks (64 fingers, P1dB of 35.7dBm) and four Building Blocks (128 fingers, P1dB of 38.2dBm).

Ultra low-noise highly linear integrated 1.5 to 2.7 GHz LNA

This paper presents a wideband, fully integrated, low-noise amplifier with a noise figure of less than 0.5 dB. The device is fabricated in a 0.35 μm GaAs enhancement-mode pHEMT process because of its positive threshold voltage and superior noise performance. The amplifier is housed in a low-cost 2×2 mm2 8-pin QFN plastic package with internal gate biasing and input and output matching. To our knowledge, this work achieved the best result of reported combination of low noise figure, OIP3 (40 dBm), and Linearity Figure of Merit (LFOM) of 15dB at a frequency range of 1.5-2.7GHz for sub-0.5 dB NF LNA, and integrated power-down function for system control.