Reduced gain variation against temperature with thermistor on HPA module for W-CDMA system
A high-power amplifier (HPA) module for wide-band code division multiple access (W-CDMA) system with small gain variation against temperature is presented in this paper. Two temperature compensation techniques, which contain gain control bias circuits that correspond to temperature or thermistors were investigated. Comparison between the above techniques indicated that the technique with thermistors was more effective in reducing gain variation without affecting linearity. A fabricated two-stage HPA module for W-CDMA system with a thermistor in its input matching network provided a small gain variation within plusmn1 dB and an ACLR under -36 dBc in the temperature range from -10 to +85degC when ACLR was measured under load mismatched conditions, VSWR=1.4:1.
Temperature dependences of current gains in GaInP/GaAs and AlGaAs/GaAs heterojunction bipolar transistors
The temperature dependences of current gain are investigated for both GaInP/GaAs and AlGaAs/GaAs heterojunction bipolar transistors (HBTs). Measured results indicate that for GaInP/GaAs HBTs the current gain at collector current densities >0.1 A/cm/sup 2/ remains nearly constant, independent of the substrate temperature for AlGaAs/GaAs HBTs. These current gain characteristics are examined, and the origin of the difference is attributed to the difference of the valence-band discontinuities in the base-emitter heterojunctions of the two HBTs. >
A 20 mA quiescent current CV/CC parallel operation HBT power amplifier for W-CDMA terminals
A novel constant voltage/constant current (CV/CC) parallel operation HBT power amplifier (PA) configuration is proposed. By combining two HBT's having different base bias circuits for each (one is CV and the other is CC), non-linearity at large back-off region can be canceled out. Therefore, both low quiescent current and enough ACPR performance can be achieved. The fabricated CV/CC parallel operation HBT PA demonstrates extremely low quiescent current of 20 mA and ACPR of less than -38 dBc at the output power range up to 27.5 dBm.