Differential amplifier, operational amplifier employing the same, and liquid crystal driving circuit incorporating the operational amplifier
AssigneeSharp Kabushiki Kaisha
InventorTomoaki Nakao
Life of this patent
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Abstract
An incidental offset voltage caused by discrepancies in material and workmanship can be averaged by (1) using two input transistors of a differential amplifier alternately, and (2) switching output signals from both the input transistors through two switches provided to an output end. Consequently, a downsized, less-power-consuming, highly-reliable differential amplifier which is insensitive to an incidental offset voltage caused by discrepancies in material and workmanship can be provided. Also, by employing such a differential amplifier, a less-power-consuming and highly reliable operational amplifier and a liquid crystal driving circuit capable of showing display of an upgraded quality can be realized.
Claims33
A differential amplifier for amplifying two kinds of input signals including a common mode input signal and a differential mode input signal, comprising:
- first and second amplifiers for amplifying said two kinds of input signals;
- and
- control means for selectively switching said two kinds of input signals to be inputted to said first and second amplifiers, said control means also outputting the common mode input signal amplified by one of said first and second amplifiers as a differential mode output signal and the differential mode input signal amplified by the other amplifier as a common mode output signal.
An operational amplifier comprising:
- an input circuit including a differential amplifier for amplifying two kinds of input signals including a common mode input signal and a differential mode input signal;
- and
- an output circuit of a CMOS structure for outputting a voltage based on an output from said input circuit, wherein said differential amplifier includes:
- first and second amplifiers for amplifying said two kinds of input signals;
- and
- control means for selectively switching said two kinds of input signals to be inputted to said first and second amplifiers, said control means also outputting the common mode input signal amplified by one of said first and second amplifiers as a differential mode output signal and the differential mode input signal amplified by the other amplifier as a common mode output signal.
A liquid crystal driving circuit having an operational amplifier for amplifying an input liquid crystal driving voltage, comprising output alternating switching means for converting an amplified liquid crystal driving voltage to an alternating voltage by switching a polarity of said amplified liquid crystal driving voltage with a switching action of an output from said operational amplifier, wherein said operational amplifier includes:
- an input circuit including a differential amplifier for amplifying two kinds of input signals including a common mode input signal and a differential mode input signal;
- and
- an output circuit of a CMOS structure for outputting
- a voltage based on an output from said input circuit, wherein said differential amplifier includes:
- first and second amplifiers for amplifying said two kinds of input signals;
- and
- control means for selectively switching said two kinds of input signals to be inputted to said first and second amplifiers, said control means also outputting the common mode input signal amplified by one of said first and second amplifiers as a differential mode output signal and the differential mode input signal amplified by the other amplifier as a common mode output signal.
Dependencies are inferred from the claim text.