Differential amplifying circuit

a technology of amplifiers and circuits, applied in the field ofdifferential amplifiers, can solve the problems of higher cost and complicated circuits of lcd driver circuits, and achieve the effect of simple circuit arrangemen

Active Publication Date: 2019-06-25
RENESAS ELECTRONICS CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The proposed solution enables high-precision output of averaged voltages, improving the accuracy of LCD driver circuits and reducing complexity, thereby minimizing costs associated with increased chip area.

Problems solved by technology

When such a higher gradation display is achieved, an LCD driver circuit becomes more complicated.
In this LCD driver, furthermore, a chip area of the driver circuit is increased, resulting in higher cost.

Method used

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  • Differential amplifying circuit
  • Differential amplifying circuit
  • Differential amplifying circuit

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first embodiment

[0041]FIG. 3 is a diagram showing a circuit arrangement of an equivalent circuit of an operational amplifier having two inputs. FIG. 4 is a circuit diagram showing a specific circuit arrangement of a PMOS (P-channel MOS) transistor differential amplifier contained in the equivalent circuit shown in FIG. 3. FIG. 5 is a circuit diagram showing another specific circuit arrangement of an NMOS (N-channel MOS) transistor differential amplifier contained in the equivalent circuit shown in FIG. 3.

[0042]The operational amplifier shown in FIG. 3 is constituted by combining the PMOS transistor differential amplifier shown in FIG. 4 and the NMOS transistor differential amplifier shown in FIG. 5. In order to easily understand the present invention, the circuit arrangement and operation of each of the PMOS transistor differential amplifier and the NMOS transistor differential amplifier will be described. Further, an equivalent circuit arranged by combining the NMOS transistor differential amplifi...

second embodiment

[0085]FIG. 9 is a diagram showing the circuit arrangement of a differential amplifier according to the second embodiment of the present invention. Referring now to FIG. 9, the differential amplifier of the second embodiment is formed from the 2-input PMOS transistor differential stage, the 2-input NMOS transistor differential stage, a current adder circuit and an amplifying unit A2. The 2-input PMOS transistor differential stage is composed of the constant current source CC2 and the PMOS transistors M1 to M4, like the PMOS transistor differential stage in the first embodiment. Also, the 2-input NMOS transistor differential stage is composed of the constant current source CC1 and the NMOS transistors M7 to M10, like the NMOS transistor differential stage in the first embodiment. The current adder circuit adds the outputs of the NMOS transistor differential stage and the outputs of the PMOS transistor differential stage, and outputs the addition result to the amplifying unit A2. The o...

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PUM

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Abstract

A differential amplifier circuit includes a first differential transistor pair, a second differential transistor pair, an adder section and an amplifying unit. The first differential transistor pair receives first and second input signals and an output signal as a third input signal, and the second differential transistor pair receives the first and second input signals and the output signal as a fourth input signal. The adder section adds first output signals from the first differential transistor pair and second output signals from the second differential transistor pair, and the amplifying unit amplifies an addition resultant signal from the adder section to output to the first and second differential transistor pairs.

Description

[0001]This is a reissue application of U.S. Pat. No. 7,170,348, which was filed as U.S. patent application Ser. No. 10 / 975,935 on Oct. 29, 2004 and issued on Jan. 30, 2007, and which claims priority from Japanese Patent Application No. 2003-373638, filed on Oct. 31, 2003 in the Japanese Intellectual Property Office, the disclosures of all of which are incorporated herein by reference in their entireties. BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a differential amplifier. More specifically, the present invention is directed to a differential amplifier used in an amplifying circuit of an LCD driver for driving a capacitive load.[0004]2. Description of the Related Art[0005]Nowadays, there is a trend that higher gradation is strongly required in a TFT-LCD (Thin-Film Transistor Liquid Crystal Display) field. That is to say, conventionally, 260,000-color display (64 gradation levels in 6 bits) sufficiently satisfied requirements of th...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): H03F3/45G09G3/36G09G3/20
CPCH03F3/45183H03F3/4521H03F2203/45682H03F3/45
InventorNISHIMURA, KOUICHISHIMATANI, ATSUSHI
OwnerRENESAS ELECTRONICS CORP