This paper discusses the non-saturating GaAs/AlGaAs N-p-n heterojunction bipolar transistor (GaAs HBT) technology and circuit applications where the GaAs HBT offers unique advantages. A relaxed 2-3 ?m emitter self-aligned HBT IC process and molecular beam epitaxial structure developed at TRW for producibility, permit simultaneous fp, fmax ? 30-60 GHz, dc current gain ??50-100, and MSI-LSI integration levels. It is used as a vehicle for demonstrating initial technology capabilities including dc to 20 GHz analog/microwave, 3-6 GHz digital, and 1-3 GHz analog/digital conversion, as well as monolithically- combined functions. Significant improvements are realized over advanced Si bipolar and GaAs field-effect transistor approaches in combinations of operational frequency, power consumption, gain-bandwidth product, harmonic distortion, phase (1/f) noise, and radiation hardness. These capabilities along with the GaAs HBT technology’s extensive growth potential should assure its future competitiveness as well as its expanding role in achieving more efficient system functions.