A pulse width modulation (PWM) digital-to-analog conversion circuit includes switches 102, 104, 114, 116 controlled by a first PWM signal, and switches 106, 108, 110, 112 controlled by a second PWM signal. A first operational amplifier (op-amp) includes a first input coupled to an output of a filter, and a second input coupled to an output of the first op-amp. During a first time period, an output of a second op-amp is coupled to an input of the filter via switches 102 and 104, and an output of a third op-amp is coupled to the output of the first op-amp via switches 114 and 116. During a second time period, the output of the second op-amp is coupled to the output of the first op-amp via switches 106 and 108, and an output of the third op-amp is coupled to the input of the filter via switches 110 and 112.

A four-terminal-pair AC quantum resistance dissemination bridge and related methods are provided. The bridge includes: a supply transformer IVD1, a Kelvin branch A1, a Wagner branch A0, the first and second current sources A2, A3, an injection inductive voltage divider A4, a ratio transformer IVD2, the first and second four-terminal AC resistor connection points Z1, Z2, chokes H, and null indicators D. An isolated inductive winding LO is wound along the ratio transformer IVD2 and supplies excitation current to primary winding of injection inductive voltage divider A4 to avoid the mutual influence among various balance networks and rapid balance of the bridge can be realized. By changing turn ratio of primary winding L3 and secondary winding L4 of the second inductive voltage divider T2, the phase shift can be realized through only one set of capacitors for imaginary part error compensation, the bridge with multiple frequency points can be obtained.

A measurement system and a method of removing effects of instability of the measurement system while measuring at least one S-parameter of a device under test (DUT) are provided. The method includes initially determining a characteristic of the measurement system, including identifying a location of an instability in the time domain of the measurement system; determining a change of the characteristic of the measurement system while connected to the DUT; and compensating for the determined change of the characteristic of the measurement system while connected to the DUT by removing effects of the determined change on measurements of the at least one S-parameter of the DUT.

A current sampling circuit with on-chip real-time calibration is used to detect the on-state current of a driving transistor. The current sampling circuit includes a first resistor, a second resistor, a voltage sampling circuit, a sampling voltage operational circuit and an on-state resistance calibration circuit. The voltage sampling circuit is used to obtain on-state voltage drop value of the driving transistor Vds. The on-state resistance calibration circuit includes a reference current source and a calibrating transistor. On-state resistance value of the calibrating transistor is set to be K1 times of on-state resistance value of the driving transistor. The on-state voltage drop value Vds obtained by the voltage sampling circuit and the on-voltage drop value of the calibrating transistor Vrsns are input to the sampling voltage operational circuit to obtain proportional relationship K2 between the on-state voltage drop value Vds and the on-state voltage drop value Vrsns.

The present invention discloses an AC impedance measurement circuit with a calibration function, which is characterized in that only one calibration impedance is needed, associated with a switch circuit. Based on the measurement results of the two calibration modes, an equivalent impedance of the switch circuit, circuit gain and phase offset can be calculated. Based on the above results, the equivalent impedance of the internal circuit is deducted from the measurement result of the measurement mode to accurately calculate an AC conductance and a phase of the AC conductance for impedance to be measured. In addition, by adjusting a phase difference between an input sine wave signal and a sampling clock signal, impedance of the same phase and impedance of the quadrature phase can be obtained, respectively, and the AC impedance and phase angle of the impedance to be measured can be calculated.

A comb signal generator that includes at least two signal sources that each provide a signal, wherein the signals provided by the at least two signal sources are shaped similarly. The comb signal generator also has a combining circuit connected with the at least two signal sources, wherein the combining circuit is configured to combine the signals provided by the at least two signal sources, thereby generating a combined signal. Further, the comb signal generator includes a clipping circuit connected with the combining circuit, wherein the clipping circuit is configured to receive and process the combined signal, thereby generating a comb signal. Further, a method of providing a phase and amplitude reference is described.

Aspects of the invention include a circuit having a power header configured to couple to a power supply and to provide an output voltage. A sense circuit is coupled to the power header to receive the output voltage, the sense circuit including a replica voltage circuit coupled to a replica power header circuit and a transistor, the replica voltage circuit being configured to provide a replicated output voltage in accordance with the output voltage, the replica power header circuit being configured to couple to the power supply and the replicated output voltage to generate a replica current, the transistor being configured to deliver the replica current.

Methods, apparatuses and systems for providing offset calibration and fault monitoring are disclosed herein. An example controller component may comprise: a resistance-based bridge circuit; a signal conditioning circuit configured to condition an output of the resistance-based bridge circuit; a first diagnostic circuit coupled to the signal conditioning circuit configured to monitor an output of a first branch of the resistance-based bridge circuit; and a second diagnostic circuit coupled to the signal conditioning circuit configured to monitor an output of a second branch of the resistance-based bridge circuit.

An encapsulated structure for a quantum resistance standard according to an embodiment of the present invention includes a base; an object disposed on the base and providing a measurement value of the quantum Hall resistance; two or more conductive lines connected to the object on one end; and a cap isolating the object from outside air.

An amplifier circuit includes: a Schmidt trigger having an input electrically coupled to an input of the amplifier circuit, a switching network electrically coupled to an output of the Schmidt trigger, an inductor electrically coupled to the switching network, a first resistor electrically coupled to the inductor, a capacitor electrically coupled to the first resistor, a first feedback circuit that provides a first feedback signal to the input of the Schmidt trigger based on a voltage at a first node electrically coupled to the first resistor and to the capacitor, a second resistor electrically coupled to the output of the amplifier circuit, a third resistor electrically coupled to the second resistor, and a second feedback circuit that provides a second feedback signal to the input of the Schmidt trigger based on a voltage at a second node electrically coupled to the second resistor and to the third resistor.