Document Type and Number:
Japanese Patent JPH0542179
Kind Code:
B2
Abstract:
An operational amplifier capable of selectively performing a variety of circuit functions is provided. A single operational amplifier utilizes switched capacitors for sampling and holding an input signal, for establishing a low frequency pole, for applying the sample to an output capacitance to charge the capacitance and for comparing the input signal with a reference. The multi-function circuit provides a large savings in circuit area and permits versatility of circuit applications. One embodiment of the invention is to utilize a companding DAC having a capacitor array which may be used as the output capacitance of the operational amplifier circuit. The DAC provided utilizes an R ladder DAC coupled directly to a C DAC and has a switching structure that is simpler than comparable prior art circuits. The DAC is asynchronous and has programmable A- and Mu-255 law PCM conversion capability. Coupled directly to the C DAC is an operational amplifier receive filter circuit which utilizes the C DAC as an input capacitor thereby eliminating the need for a buffer amplifier and allowing the DAC to be used for both analog to digital and digital to analog conversion.
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Inventors:
KELLEY STEPHEN HARLOW (US)
ULMER RICHARD WALTER (US)
ULMER RICHARD WALTER (US)
Application Number:
JP50172582A
Publication Date:
June 25, 1993
Filing Date:
April 21, 1982
Export Citation:
Assignee:
MOTOROLA INC (US)
International Classes:
H03M1/00; H03M1/80; H03H19/00; (IPC1-7): H03M1/80; H03H19/00
Domestic Patent References:
| JPS5538796A | 1980-03-18 |
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