公开(公告)号：CA1171967A

公开(公告)日：1984-07-31

申请号：CA400925

申请日：1982-04-14

Applicant: MOTOROLA INC

Inventor： ALLGOOD ROBERT N ,  KELLEY STEPHEN H

IPC: H03H19/00 ,  H03M1/00 ,  H03M1/66 ,  H03K13/11

Abstract: DIGITAL TO ANALOG CONVERTER 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.

公开(公告)号：CA1172709A

公开(公告)日：1984-08-14

申请号：CA401184

申请日：1982-04-19

Applicant: MOTOROLA INC

Inventor： ALLGOOD ROBERT N ,  KELLEY STEPHEN H ,  ULMER RICHARD W ,  WURZBURG HENRY

IPC: H03F1/34 ,  H03F1/30 ,  H03H19/00 ,  H03M1/12

Abstract: A MULTIPLE FUNCTION OPERATIONAL AMPLIFIER CIRCUIT 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 Aand 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.