Differential Temperature Sensor with Sensitivity Set by Current-Mirror and Resistor Ratios without Limiting DC Bias

• Main Authors: CHAN KAM HUNG, WONG CHUN FAI, KWONG KWOK KUEN (DAVID), PUN LEUNG LING (ALAN)
• Format: Patent
• Language: English
• Published: 11.12.2014
• Subjects: ELECTRICITY; MEASURING; MEASURING QUANTITY OF HEAT; MEASURING TEMPERATURE; PHYSICS; TESTING; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR

A differential on-chip temperature sensor circuit can be implemented in a standard complementary metal-oxide-semiconductor (CMOS) process using PNP transistors. A pair of transistors have collector currents that are sensitive to voltage, both directly and due to saturation currents. A scaling resistor connects to the emitter of one transistor and its voltage compared to the other transistor's emitter voltage by an error amplifier that generates a bias voltage to current sources that are proportional to absolute temperature since the saturation current sensitivity is subtracted out. The current is mirrored to sink current through a multiplier resistor from an output. An amplifier connected across the multiplier resistor compares a reference voltage to set the DC bias independent of temperature sensitivity. The temperature sensitivity is proportional to the ratio of the multiplier resistor and the scaling resistor, and is multiplied by a mirroring factor. A differential output is provided.