Transit time effect in high-frequency characteristics of HBTs

Seonghearn Lee, Anand Gopinath

Research output: Contribution to journalArticlepeer-review


Multiple negative resistance bands are predicted at frequencies beyond fmax in the conventional mesa-type emitter-up AlGaAs/GaAs HBTs (heterojunction bipolar transistors) with careful design and reduced parasitics. Thus, HBT power gain may be obtained in these frequency bands with the negative resistance even above fmax. To obtain the usable transit time effect with large negative resistance, the increase of collector transit time is preferable to increasing base transit time. Therefore, for transit time HBTs, the base should be designed to be as thin as possible, and the collector should be thick enough to obtain the large transit time in the frequency range of interest, while keeping parasitics small.

Original languageEnglish (US)
Pages (from-to)271-272
Number of pages2
JournalIEEE MTT-S International Microwave Symposium Digest
StatePublished - Jun 1 1992


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