Abstract: A temperature sensing circuit using CMOS switch-capacitor includes a PNP BJT, a hysteresis comparator, a transconductance amplifier, two current sources, two capacitors, and six switches. A voltage complementary to the absolute temperature (CTAT) is generated according to the PNP BJT, and a voltage proportional to the absolute temperature (PTAT) is generated according to two capacitors and the transconductance amplifier. When the voltage proportional to absolute temperature is greater than the voltage complementary to absolute temperature as the temperature rising, the hysteresis comparator outputs a high level signal.

Abstract: A clamp circuit comprises a first transistor, a second transistor and a voltage-dividing circuit. The first transistor has a source terminal connected to a reference voltage, and has a drain terminal grounded through a current source. The second transistor has a gate terminal connected to the gate and drain terminals of the first transistor, and has a drain terminal grounded. The voltage-dividing circuit is connected to an input voltage end, an output voltage end and a source terminal of the second transistor for providing a clamping voltage.