Transistor junction monitors remote temperature

摘要

The circuit in Figure 1 uses a regular, general-purpose transistor as the sensing element and a thermal-diode monitor IC to measure temperature. The ADM1021 usually connects to an on-chip thermal diode on a CPU die itself, but in this application the sensor connects to a regulator low-cost discrete npn transistor, the 2N3904. The circuit ties the transistor base and collector together to form a two-wire sensor.