Reference current generation circuit

The present invention discloses a reference current generating circuit. By the circuit C, D points increase a unity gain amplifier, so that current I4 does not vary with temperature; by adjusting the ratio between the PMOS transistor of the third PMOS transistor (407) and a first PMOS transistor (408), such that the first PNP equal to the collector current of transistor (403) and the third PNP transistor (409) of. By improving these two places, so that the current I3 can completely offset the higher-order terms of reference current. By simulation, the improved circuit can be a temperature characteristic reaches 0.5ppm / ℃ reference current.