Low-noise, low power dissipation GaAs monolithic broad-band amplifiers

GaAs monolithic amplifiers with low noise and low dc power dissipation developed for VHF-UHF mobile radio systems are discussed. The amplifiers have a two-stage construction, the gate width for the first stage being 1000 microns and that for the second stage being 500 microns. With this circuit configuration, both the noise figure and the bandwidth are improved. It is noted that to maintain the uniformity for the ion-implanted active layers and to reduce the gate source resistance and gate-drain resistance, a 'closely spaced electrode FET' was adopted. The FET makes possible low drain voltage operation, which in turn results in low dc power dissipation. The amplifier developed for an FET threshold voltage of -0.6 V provides a 3-dB noise figure, less than 170-mW dc power dissipation, a bandwidth of 9 MHz-3.9 GHz, and a gain of 16 dB. It is able to operate under a unipolar power source, and when external choke inductors are introduced for the amplifier, power dissipation of 120 mW dc is achieved.