Temperature setpoint circuit with hysteresis

A temperature setpoint circuit comprises bipolar transistors Q 1 and Q 2 which receive currents I 1 and I 2 at their respective collectors and are operated at unequal current densities, with a resistance R 1 connected between their bases such that the difference in their base-emitter voltages (Delta...

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Bibliographische Detailangaben
Hauptverfasser:	TRAN CHAU C, BROKAW A. P
Format:	Patent
Sprache:	eng
Schlagworte:	BLASTING COMBUSTION APPARATUS COMBUSTION PROCESSES CONTROLLING HEATING LIGHTING MECHANICAL ENGINEERING PHYSICS REGULATING REGULATING OR CONTROLLING COMBUSTION SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES WEAPONS
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Beschreibung
Zusammenfassung:	A temperature setpoint circuit comprises bipolar transistors Q 1 and Q 2 which receive currents I 1 and I 2 at their respective collectors and are operated at unequal current densities, with a resistance R 1 connected between their bases such that the difference in their base-emitter voltages (DeltaVbe) appears across R 1 . An additional PTAT current I 3 is maintained in a constant ratio to I 1 and I 2 and provided to the collector of Q 2 while Q 2 is off, and is not provided while Q 2 is on. The circuit is arranged such that Q 2 is turned on and conducts a current equal to Ia when: DeltaVbe=(kT/q)ln(NI 1 /Ia), where Ia=I 2 +I 3 , the temperature T at which DeltaVbe=(kT/q)ln(NI 1 /Ia) being the circuit's setpoint temperature, such that the switching of current I 3 provides hysteresis for the setpoint temperature which is approximately constant over temperature.