75 Years of RF Design: Highlights and Paradigm Shifts

Radio-frequency (RF) circuits came into existence decades before the invention of the transistor. The First World War motivated great advances in wireless communications and radar design—all based on vacuum tubes. Then came the notion of public radio and television, driving RF circuits into the consumer market. By the mid-1940s, when the bipolar transistor was conceived at Bell Laboratories, vacuum-tube RF design had become fairly mature
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. Of course, the products drew high power and failed frequently. Based on electron transport in a vacuum, these components could operate as only “n-type” devices, a stark contrast to what bipolar and MOS technologies would offer decades later.