A 4-GHz 12-W transistor amplifier utilizing a self-aligned bipolar structure

Abstract

A HIGH-POWER three-stage transistor amplifier utilizing a bipolar transistor, which can deliver 12W output power at 4 GHz, will be described. The amplifier, exhibiting power gain of l l l3dB, power added efficiency of 17%, and can operate with a 20-V dc power supply, contains seven units of a 3-W bipolar transistor, fabricated with self-aligned electrode formation technology’. Figure 1 shows the block diagram of the amplifier circuit. Each transistor amplifier segment contains input and output matching networks of the microstripline type, and is connected to the power combiner/divider of a double section 3dB quarter wavelength hybrid. Teflon glass-fiber substrates have been used for the matching networks and for the hybrid couplers. In Figures 2 (a) and (b) RF performance characteristics i.e., output power, efficiency and AM-PM conversion coefficient versus input power, and output power versus frequency characteristics at different ambient temperatures are shown. The noise loading characteristics are also satisfactory.