Fujitsu Corporation

Fujitsu Semiconductor Limited

Akiyoshi Matsuda

Tsunehiko Moriuchi

Hiroko Haraguchi

Akihiro Suzuki

An output circuit includes first to fourth transistors, first and second constant current units, and a differential pair. The gates of the first and second transistors are supplied with two input signals, respectively. The drain of the first transistor is coupled to the drain of the third transistor and the gate of the fourth transistor. The drain of the second transistor is coupled to the gate of the third transistor and the drain of the fourth transistor. The first constant current unit is coupled to the sources of the third and fourth transistors. The differential pair includes two transistors, and the gates of the two transistors are coupled to the drains of the first and second transistors, respectively. The second constant current unit is coupled to the sources of the two transistors. Two output signals are output from two nodes respectively corresponding to the drains of the two transistors.

Output circuit

A differential amplifier of the present invention comprises transistors where to each of which one of two inputs to said differential amplifier is provided; current mirror circuits where each of which delivers one of the outputs of the differential amplifier to the load side; and cut-off prevention units where each of which is connected to the connecting point of a transistor to which a monitor current of one of the current mirror circuits flows, and one of the transistors to which the inputs are provided, and applies a current for preventing cutting off the transistor to which the monitor current flows, when the input to the transistor to which the input is provided is L.

Differential amplifier

A differential amplifier for amplifying an input signal at a constant amplification rate regardless of fluctuation in the center voltage of the input signal. The differential amplifier includes a first differential pair operated when a complementary input signal is greater than or equal to an intermediate level between power supplies. A second differential pair is operated when the complementary input signal is less than or equal to an intermediate level of the power supplies. A current synthesizing circuit synthesizes output currents of the first and second differential pairs to generate output voltage. An output current offset circuit offsets a current corresponding to the output current of one of the differential pairs based on the complementary input signal so that the output voltage becomes the output current of one of the first and second differential pairs.

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Kasugai, Japan

Akiyoshi Matsuda