Voltage reference circuit

The invention discloses a voltage reference circuit. On the basis of the conventional common band gap reference voltage source circuit structure, a fixed bias circuit and a starting and over-voltage protection circuit are arranged; monoploid bipolar transistor base emitter PN junction voltage VBE and diploid bipolar transistor base emitter PN junction voltage 2VBE are realized in the fixed bias circuit; comparison control between the bipolar transistor base emitter PN junction voltage and reference voltage output by a band gap reference voltage source is realized through the starting and over-voltage protection circuit, so the output reference voltage during the normal work of the band gap reference voltage source is defined in a safe range; when the output reference voltage is over-high,automatic protection of the circuit can be realized; and the circuit has a simple structure and is suitable to be manufactured by the various bipolar transistor and metal oxide field effect transistor compatible processes.