A Two-Gain-Stage Amplifier without an On-Chip Miller Capacitor in an LCD Driver IC

Tetsuro ITAKURA  Hironori MINAMIZAKI  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E85-A   No.8   pp.1913-1920
Publication Date: 2002/08/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Analog Signal Processing
Keyword: 
analog signal processing,  integrated electronics,  phase compensation,  amplifier,  LCD driver,  

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Summary: 
An LCD Driver IC includes more than 300 buffer amplifiers on a single chip. The phase compensation capacitors (on-chip Miller capacitors) for the amplifiers are more than 1000 pF and occupy a large chip area. This paper describes a two-gain-stage amplifier in which an on-chip Miller capacitor is not used for phase compensation in an LCD Driver IC. In the proposed amplifier, phase compensation is achieved only by a newly introduced zero, which is formed by the load capacitance and a phase compensation resistor connected between the output of the amplifier and the capacitive load. Designs of the phase compensation resistor and the amplifier before compensation are discussed, considering a typical load capacitance range. The test chip was fabricated. The newly introduced zero successfully stabilized the amplifier. The chip area for the amplifier was reduced by 30-40%, compared with our previously reported one. The current consumption of the amplifier was only 5 µA. The experimental results of the fabricated test chip support that the proposed amplifier is suitable to an LCD driver IC with a smaller chip area.