PURPOSE: To provide a current source with a high output impedance, a highly accurate current mirror circuit and an A/D conversion circuit with high accuracy and low power consumption.
CONSTITUTION: A source of a MOS transistor(TR) M1 is connected to a power supply VDD and its gate receives a voltage VB1. The device is provided with the MOS TR M1, an operational amplifier 1 whose inverting input terminal connects to a drain of the MOS TRM1 and whose noninverting input terminal receives a voltage VB2, and a MOS TR M2 whose gate receives an output of the operational amplifier and whose source is connected to the drain of the TR M2, and they form a constant current source using the drain of the TR M2 as a current output terminal. A constant current flows to an imaginary ground of the operational amplifier without changing a drain voltage of the MOS TR M1 deciding the current even when a voltage at the current output terminal is subjected to change and then the current source with a high impedance is realized. A highly accurate current mirror is obtained by selecting drain voltages of the current mirror pair identically as an imaginary ground similarly to above.
| JPH07106969 | A/D CONVERTER |
| JPS5493349 | LOGARITHMIC COMPRESSION AD CONVERTER |
| JPH08107354 | PIPELINE TYPE SUCCESSIVE APPROXIMATION A/D CONVERTER |
YAMAKIDO KAZUO
OKAZAKI TAKAO
NISHIKAWA NORIMITSU
KOBAYASHI YOICHIRO
