Bandgap reference voltage circuit with PTAT current source

摘要

A bandgap reference circuit capable of operating at low voltage provides an adjustable bandgap reference voltage. The bandgap reference circuit includes a proportional to absolute temperature (PTAT) current source, a bias current source, two resistors and a transistor. The base of the transistor couples to the IPTAT current source and the emitter of the transistor couples to the bias current source. The bandgap reference circuit also includes two resistors. The first resistor couples between the emitter and the base of the transistor, and the second resistor couples to the base of the transistor. The first resistor receives a portion of the bias current and provides a current proportional to a base- emitter voltage of the transistor. The second resistor receives the PTAT current and the current proportional to the base-emitter voltage of the transistor and provides a reference voltage which remains substantially constant over temperature and which is proportional to a silicon bandgap voltage. The ratio of the first and second resistors determines the proportionality of the reference voltage to the silicon bandgap voltage. Thus, by adjusting the ratio of the two resistors a reference voltage less than the silicon bandgap voltage can be obtained.