Patent
1986-11-19
1988-04-19
James, Andrew J.
357 43, 357 46, 357 22, 357 86, H01L 2972
Patent
active
047393866
ABSTRACT:
Switching off time of a bipolar transistor is improved. When the bipolar transistor is driven to a saturation condition, the collector voltage does not go up rapidly when it is switched off again, because once the collector voltage is much less than the base voltage, reverse injection occurs, so the collector voltage can not follow the base voltage until the reverse injected electrons are swept out. In order to avoid saturation, a vertical FET is provided between the base and collector of the bipolar transistor to clamp the base-collector voltage. The channel region of the vertical transistor is formed between the base contact region and collector region of the transistor. Thus, when the transistor is in a non-saturation state, the channel is closed by built in potential, but when the transistor approaches the saturation state, the channel automatically opens to shunt between the base and collector of the bipolar transistor. By replacing a Shottky barrier diode used in prior art circuits for such purposes, with a vertical FET, the device becomes more resignable, and fabrication process is simplified.
REFERENCES:
patent: 4095252 (1978-06-01), Ochi
patent: 4143392 (1979-03-01), Mylroie
patent: 4337474 (1982-06-01), Yukimoto
patent: 4613887 (1986-09-01), Fukuda
patent: 4689651 (1987-08-01), Hanna
IBM Technical Disclosure Bulletin, vol. 15, #9, Feb. 1973, by Lewis.
Fujitsu Limited
James Andrew J.
Prenty Mark
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