Traditionally, microwave circuit designers interested in exploiting these frequencies have turned to discrete components, despite the expense of assembling and packaging them and the dearth of buyers that can afford the result. Today this scenario was rapidly being transformed by indium phosphide heterojunction bipolar transistors (HBTs), a technology that was currently yielding large-scale integrated (LSI) circuits packing 1000 to 10000 transistors on a chip and operating at over 65 GHz. Success in integrating such fast, dense transistors have bred numerous analog, digital, and mixed-mode ICs having unprecedented performance.