A thermally-isolated-metal-oxide-semiconducting (TMOS) sensor has inputs coupled to first and second nodes to receive first and second bias currents, and an output coupled to a third node. A tail has a first conduction terminal coupled to the third node and a second conduction terminal coupled to a reference voltage. A control circuit applies a control signal to a control terminal of the tail transistor based upon voltages at the first and second nodes so that a common mode voltage at the first and second nodes is equal to a reference common mode voltage. A differential current integrator has a first input terminal coupled to the second node and a second input terminal coupled to the first node, and provides an output voltage indicative of an integral of a difference between a first output current at the first input terminal and a second output current at the second input terminal.

A quad signal generator circuit generates four 2.sup.N−1 bit control signals in response to a sampling clock and a 2.sup.N−1 bit thermometer coded signal. A digital-to-analog converter (DAC) circuit has 2.sup.N−1 unit resistor elements, with each unit resistor element including four switching circuits controlled by corresponding bits of the four 2.sup.N−1 bit control signals. Outputs of the 2.sup.N−1 unit resistor elements are summed to generate an analog output signal. The quad signal generator circuit controls generation of the four 2.sup.N−1 bit control signals such that all logic states of bits of the four 2.sup.N−1 bit control signals remain constant for at least a duration of one cycle of the sampling clock. The analog output signal may be a feedback signal in a sigma-delta analog-to-digital converter (ADC) circuit that includes a multi-bit quantization circuit operating to quantize a filtered loop signal to generate the 2.sup.N−1 bit thermometer coded signal.

A quad signal generator circuit generates four 2.sup.N−1 bit control signals in response to a sampling clock and a 2.sup.N−1 bit thermometer coded signal. A digital-to-analog converter (DAC) circuit has 2.sup.N−1 unit resistor elements, with each unit resistor element including four switching circuits controlled by corresponding bits of the four 2.sup.N−1 bit control signals. Outputs of the 2.sup.N−1 unit resistor elements are summed to generate an analog output signal. The quad signal generator circuit controls generation of the four 2.sup.N−1 bit control signals such that all logic states of bits of the four 2.sup.N−1 bit control signals remain constant for at least a duration of one cycle of the sampling clock. The analog output signal may be a feedback signal in a sigma-delta analog-to-digital converter (ADC) circuit that includes a multi-bit quantization circuit operating to quantize a filtered loop signal to generate the 2.sup.N−1 bit thermometer coded signal.

Some embodiments of the invention may include an eddy current nondestructive evaluation device. The eddy current nondestructive evaluation device may include a rotating body; a motor coupled with the rotating body such that the motor rotates the rotating body; a permanent magnet coupled with the rotating body; a pickup coil coupled with the rotating body; and an integrator circuit electrically coupled with the pickup coil that integrates a voltage from the pickup coil to produce integrated voltage data.

An amplification interface includes a drain of a first FET connected to a first node, a drain of a second FET connected to a second node, and sources of the first and second FETs connected to a third node. First and second bias-current generators are connected to the first and second nodes. A third FET is connected between the third node and a reference voltage. A regulation circuit drives the gate of the third FET to regulate the common mode of the voltage at the first node and the voltage at the second node to a desired value. A current generator applies a correction current to the first and/or second node. A differential current integrator has a first and second inputs connected to the second and first nodes. The integrator supplies a voltage representing the integral of the difference between the currents received at the second and first inputs.

An amplification interface includes a drain of a first FET connected to a first node, a drain of a second FET connected to a second node, and sources of the first and second FETs connected to a third node. First and second bias-current generators are connected to the first and second nodes. A third FET is connected between the third node and a reference voltage. A regulation circuit drives the gate of the third FET to regulate the common mode of the voltage at the first node and the voltage at the second node to a desired value. A current generator applies a correction current to the first and/or second node. A differential current integrator has a first and second inputs connected to the second and first nodes. The integrator supplies a voltage representing the integral of the difference between the currents received at the second and first inputs.

An A/D converter includes: a sampler that includes a sampling capacitor and samples an input signal; a D/A converter that selectively outputs an analog voltage; an integrator that integrates an input from the sampler and an input from the D/A converter; Multiple switches that include a first switch independently connecting the sampler to the integrator, a second switch independently connecting the D/A converter to the integrator, a third switch, and, a fourth switch, a quantizer that quantizes an output of the integrator; a control circuit that outputs a digital value based on an output of the quantizer, and a reference potential generation circuit that provides a second reference potential to an integrator side of the sampler through the third switch and provides a first reference potential to the integrator side of the D/A converter through the fourth switch.

An A/D converter includes: a sampler that includes a sampling capacitor and samples an input signal; a D/A converter that selectively outputs an analog voltage; an integrator that integrates an input from the sampler and an input from the D/A converter; Multiple switches that include a first switch independently connecting the sampler to the integrator, a second switch independently connecting the D/A converter to the integrator, a third switch, and, a fourth switch, a quantizer that quantizes an output of the integrator; a control circuit that outputs a digital value based on an output of the quantizer, and a reference potential generation circuit that provides a second reference potential to an integrator side of the sampler through the third switch and provides a first reference potential to the integrator side of the D/A converter through the fourth switch.

A quad signal generator circuit generates four 2.sup.N−1 bit control signals in response to a sampling clock and a 2.sup.N−1 bit thermometer coded signal. A digital-to-analog converter (DAC) circuit has 2.sup.N−1 unit resistor elements, with each unit resistor element including four switching circuits controlled by corresponding bits of the four 2.sup.N−1 bit control signals. Outputs of the 2.sup.N−1 unit resistor elements are summed to generate an analog output signal. The quad signal generator circuit controls generation of the four 2.sup.N−1 bit control signals such that all logic states of bits of the four 2.sup.N−1 bit control signals remain constant for at least a duration of one cycle of the sampling clock. The analog output signal may be a feedback signal in a sigma-delta analog-to-digital converter (ADC) circuit that includes a multi-bit quantization circuit operating to quantize a filtered loop signal to generate the 2.sup.N−1 bit thermometer coded signal.

A quad signal generator circuit generates four 2.sup.N−1 bit control signals in response to a sampling clock and a 2.sup.N−1 bit thermometer coded signal. A digital-to-analog converter (DAC) circuit has 2.sup.N−1 unit resistor elements, with each unit resistor element including four switching circuits controlled by corresponding bits of the four 2.sup.N−1 bit control signals. Outputs of the 2.sup.N−1 unit resistor elements are summed to generate an analog output signal. The quad signal generator circuit controls generation of the four 2.sup.N−1 bit control signals such that all logic states of bits of the four 2.sup.N−1 bit control signals remain constant for at least a duration of one cycle of the sampling clock. The analog output signal may be a feedback signal in a sigma-delta analog-to-digital converter (ADC) circuit that includes a multi-bit quantization circuit operating to quantize a filtered loop signal to generate the 2.sup.N−1 bit thermometer coded signal.