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US 6,633,246 B1Granted
Converter circuit with reduced area switch compensation resistance
AssigneeAnalog Devices, Inc.
InventorDerek F. Bowers
Life of this patent
Estimating the term…
Abstract
Unwanted voltage drops associated with the bit switches of a DAC are compensated with an output amplifier circuit for the DAC that includes a feedback circuit with a switch compensation resistance element that is connected in a combined series/parallel circuit with a feedback resistance circuit, so as to reduce both the size and associated capacitance of the resistance element.
Claims33
A digital-to-analog converter (DAC), comprising:
- a voltage supply terminal,
- a multi-bit decrementing resistance network connected to said terminal and having resistance elements with temperature coefficients of resistance (TCR) within a first range,
- respective switches for the bits of said network, said switches having associated resistances with TCRs within a second range different from said first range,
- an output amplifier connected to receive an output signal from said resistance network, and
- a feedback circuit for said amplifier, comprising a compensation resistance element having a TCR within said second range for said resistances associated with said switches and connected in a combined series/parallel circuit with a feedback resistance circuit having a TCR within said first range for said resistance elements of said decrementing resistance network, said feedback circuit having an effective resistance with a TCR within said first range and approximately equal to a desired feedback resistance (Rfb) for said amplifier, and an effective resistance with a TCR within said second range to at least approximately compensate for voltage drops across said switches.
2 more elements
A digital-to analog converter (DAC), comprising:
- a voltage supply terminal,
- a multi-bit decrementing resistance network connected to said terminal,
- respective switches for the bits of said network, said switches having respective associated resistances,
- an output amplifier connected to receive an output signal from said resistance network, and
- a feedback circuit for said amplifier, comprising a continuously ON compensation switch of similar type as said resistance network switches and having a resistance approximately equal to four times the resistance of the switch for the most significant bit in said resistance network, a first feedback resistance unit connected in a series circuit with said compensation switch, and a second feedback resistance unit connected in parallel with said series circuit, said first and second feedback resistance units each having a resistance approximately equal to twice a desired feedback resistance (Rfb) for said amplifier.
2 more elements
An output amplifier circuit, comprising:
- an operational amplifier (op amp) having a non-inverting input for connection to a reference voltage level, an inverting input for receiving an input signal, and an output, and
- a feedback circuit connected between the output and inverting input of said op amp, said feedback circuit comprising a resistance element having a temperature coefficient of resistance (TCR) within one range and connected in a combined series/parallel circuit with a feedback resistance circuit having a TCR within another range different from said one range, said feedback circuit having an effective resistance with a TCR within said other range for said feedback resistance circuit and approximately equal to a desired feedback resistance (Rfb) for said op amp.
An output amplifier circuit, comprising:
- an operational amplifier (op amp) having a non-inverting input for connection to a reference voltage level, an inverting input for receiving an input signal, and an output, and
- a feedback circuit connected between the output and inverting input of said op amp, said feedback circuit comprising a continuously ON switch having an associated resistance, a first feedback resistance unit connected in a series circuit with said switch, and a second feedback resistance unit connected in parallel with said series circuit, said first and second feedback resistance units each having a resistance approximately equal to twice a desired feedback resistance (Rfb) for said amplifier.
Dependencies are inferred from the claim text.