PHEMT Preamp

for 13 cm

Reprinted from Dubus lechnik IV, Preamps and Receivers

By Rainer Bertelsmeier, DJ9BV

Abstract

A preamp equipped with a PHEMT provides top-notch performance in noise figure and gain as well as unconditional stability for the 13-cm band. Noise figure is 0.35 dB at a gain of 15 dB. It utilizes the NEC NE42484A C-band PHEMT and provides a facility for an optional second stage on board. The second stage, with the new HP GaAsMMIC MGA86576, can boost the gain to about 40 dB in one enclosure. The preamp is rather broad-banded and usable from 2300 to 2450 MHz.

Circuit

The construction of this LNA follows a proven 23-cm HEMT-LNA design us-

Glucksburger Str 20 D-22769 Hamburg Germany ing a wire loop with an open stub as an input circuit.1

The FET's grounded source requires a bias circuit to provide the negative voltage for the gate. A special active bias circuit (see "Bias Circuit for Grounded Source HEMTs") is integrated into the RF board, which provides regulation of voltage and current for the FET.

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