GaAs field-effect transistors with a Schottky-barrier gate have been investigated in the frequency range 12-20 GHz. Measurements of the maximum available gain have shown that the devices have much higher gain in this range than has been expected. A 17 GHz oscillator having an output power of 4 mW and a 4-stage 14 9 GHz amplifier with 16 dB of power gain have been built using stripline technique. © 1971, The Institution of Electrical Engineers. All rights reserved.