US Patent 7150561 Zero temperature coefficient (TC) current source for diode measurement

A method and circuit for reducing a temperature dependent error in p-n junction based temperature measurements. The temperature-dependent error may be caused by parasitic resistance in a p-n junction and temperature dependent variation of a bias current in a temperature sensor. A difference in base-emitter voltage of a sensing transistor is employed to determine a temperature of a source device. In one embodiment, a zero Temperature Coefficient (TC) current source employing a temperature dependent variation of a current generates by an emitter-base voltage across a resistor between the emitter and the base of a junction transistor is used to counter balance a Proportional To Absolute Temperature (PTAT) current source.