Cascode MOS current mirror with lateral bipolar junction transistor to enhance ouput signal swing

摘要

A MOS transistor current mirror having a low output voltage is described. A first and second MOST's have their drains and gates connected respectively to form MOS diodes. The drain of the first MOST is connected to a control constant current source and the source of first MOST is connected to the drain of the second MOST. The drain and gate of the first MOST are connected to the base of a bipolar junction transistor (BJT). The collector of the BJT is connected to a first power supply line and the emitter is connected to the gate of a third MOST. A resistor is connected between the emitter of the BJT and the a second power supply line. The gate and drain of the second MOST is connected to the gate of a fourth MOST. The sources of the second and fourth MOST's are connected to the second power supply line. The drain of the fourth MOST is connected to the source of the third MOST. The drain of the third MOST is connected to external circuitry. The voltage developed between the drain of the third MOST and the second power supply line is relatively small to allow the voltage developed by the external circuitry to be relatively large, while said current mirror is providing a constant current to said external circuitry.