Abstract: A circuit for alternatively controlling a current through a device and permitting measurement of a voltage across the device or controlling a voltage across the device and permitting measurement of a current through the device includes a sense impedance in series combination with the device, an error amplifier selectable to control the controlled current or voltage, the error amplifier providing an error signal for the control, and a floating buffer driving the series combination in response to the error signal.

Abstract: A multislope A/D converter is presented which employs a multislope integration technique enabling the use of a single comparator to detect polarity changes in the integrator output voltage. The run-up interval of the integrating A/D converter is controlled by a four-step pattern that is repeated as many times as is required in order to keep the integrator output voltage within the confines of a preselected voltage range. During the first step of the four-step pattern, a positive reference charge is applied to the integrator. In the second step, a decision is made as to whether to either maintain the application of the positive reference charge to the integrator or to change over to the negative reference charge. The decision is determined such that the reference charge causes the integrator output voltage to move toward or through a preselected target voltage range.

Abstract: A continuously integrating analog-to-digital converter (ADC) calculates a digital output by integrating an input voltage over a number of time intervals using a multisloping technique to define the input voltage in terms of a slope count. A residue ADC is used in lieu of a run-down interval of the integrator to calculate the least significant bits of the ADC digital output. This is accomplished by first sampling the integrator output voltage, and then after a number of time intervals, sampling the integrator output voltage a second tune. The difference between the two residue voltages is converted into a fractional slope count by multiplication with a calibration constant. The fractional slope count can then be added to the slope count from the integrator, so that the resulting total slope count is directly proportional to the input voltage at a high resolution.

Abstract: An arrangement of switches and resistors for switching current into the summing node of an integrator uses a pair of switches for each resistor. Each resistor is connected at one end to a reference voltage. The other end of the resistor is connected to a first switch, which is in turn connected to the summing node. A second switch is connected between ground and the junction of the resistor and the first switch. One or the other of the two switches will always be on. When the first switch is on and the second one is off a current will flow from the reference voltage, through the resistor and into the summing node. When the first switch is off and the second one is on essentially the same current will flow from the reference voltage, through the resistor and into ground. The current will be nearly the same, since the virtual ground of the integrator approximates actual ground.