Constant current-constant voltage circuit

Details Constant current-constant voltage circuit Constant current-constant voltage circuit

1990-09-05

1991-09-10

Wong, Peter S.

Electricity: power supply or regulation systems

Self-regulating

Using a three or more terminal semiconductive device as the...

323315, 323907, G05F 324

Patent

active

050477064

ABSTRACT:
In a constant current-constant voltage circuit disclosed herein, gates of MOSFETs Q.sub.1 and Q.sub.2 are connected together, and the gate of the MOSFET Q.sub.1 is connected to the drain thereof. Further, the source of the MOSFET Q.sub.1 is connected to ground potential GND whereas the source of the MOSFET Q.sub.2 is connected to the drain of a MOSFET Q.sub.3 having a gate connected to power supply voltage V.sub.DD and a source connected to the ground voltage GND. A current mirror circuit including Q.sub.4 and Q.sub.5 has an input and an output respectively connected to the drain of the second MOSFET Q.sub.2 and the drain of the first MOSFET Q.sub.1. A first coefficient (W.sub.3 L.sub.2 /L.sub.3 W.sub.2) depending upon channel lengths (L.sub.2, L.sub.3) and channel widths (W.sub.2, W.sub.3) of the MOSFETs Q.sub.2 and Q.sub.3 is set at a value not larger than a predetermined value. Therefore, the MOSFET Q.sub.3 operates in a linear region as high resistance, and the MOSFETs Q.sub.1 and Q.sub.2 operate in a sub-threshold region. As a result, the dependence upon temperature is significantly improved.

REFERENCES:
patent: 4446383 (1984-05-01), Concannon et al.
patent: 4454467 (1984-06-01), Sakaguchi
patent: 4654578 (1987-03-01), Salerno et al.
patent: 4694199 (1987-09-01), Goetz
patent: 4769589 (1988-09-01), Rosenthal
patent: 4935690 (1990-06-01), Yan

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