Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Patent
1995-04-19
1996-12-31
Nelms, David C.
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
327538, 327541, 327576, 323315, H01L 3500, G05F 110, G05F 316
Patent
active
055897924
ABSTRACT:
A resistor programmable temperature switch for indicating that a preselected trip temperature has been reached includes first and second bipolar trasistors of like polarity having a fixed ratio of emitter areas; means for connecting the emitters of the first and second transistors to a common terminal; first and second current sources for providing first and second predetermined currents to the collector of the first and second transistors, respectively; a third transistor; means connecting its control terminal to the first current source and a first load terminal connected to the base of the first transistor for operating the first transistor to conduct the first predetermined current from the current source; means for interconnecting a second load terminal of the third transistor with a power supply terminal; a resistor network including first and second resistors connected between the base of the first transistor and the common terminal for biasing the base of the second transistor to a fraction of the base emitter voltage of the first transistor; and a fourth transistor; means for connecting the first load terminal of the fourth transistor to the common terminal and means for connecting the control terminal of the fourth transistor to the second current source; the load current of the fourth transistor changing state when the preselected trip temperature has been reached.
REFERENCES:
patent: 4380706 (1983-04-01), Wrathall
patent: 4633165 (1986-12-01), Pietkiewicz et al.
patent: 4885525 (1989-12-01), Gontowski, Jr.
patent: 5394078 (1995-02-01), Brokaw
Analog Devices Inc.
Nelms David C.
Phan Trong
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