A method of DAC mismatch calibration in a SAR ADC is disclosed. In one aspect, the method comprises determining a number of bits of an analog input signal (V.sub.IN), detecting if a binary code determined from the analog input signal (V.sub.IN) matches at least one trigger code, using at least one setting code to determine a calibration residue signal (V*.sub.RES) and a calibration bit (B*.sub.LSB), analyzing a least significant bit of the digital signal (C.sub.OUT) and the calibration bit (B*.sub.LSB), determining an indication of a presence of DAC mismatch, and calibrating the DAC mismatch. As the determination of the calibration bit (B*.sub.LSB) requires only one additional comparison, when compared to the normal operation, the normal operation does not need to be interrupted. Therefore, the calibration can be done in the background and, as such, can be performed frequently thereby taking into account time-varying changes due to environmental effects.

Exemplary embodiments of the present invention pertain to circuitry provided in a digital-to-analog converter (DAC) for carrying out measurements indicative of various performance characteristics of the DAC. In one exemplary implementation, a control circuit containing one or more switches is used to controllably route into a measurement system, a portion of a signal that straddles a boundary between a first digital data bit and a second digital data bit in a sequence of digital data bits that are received in a DAC cell of the DAC. The control circuit, which can be included in one or more DAC cells of the DAC, is connected to a branch of a differential circuit that is provided in each of the DAC cells of the DAC, in a manner that does not affect digital-to-analog conversion in the DAC cells.

An integrated circuit (IC) includes: a first functional analog pin or pad; a first analog test bus coupled to the first functional analog pin or pad; first and second analog circuits coupled to the first analog test bus; and a test controller configured to: when the IC is in a functional operating mode, connect an input or output of the first analog circuit to the first analog test bus so that the input or output of the first analog circuit is accessible by the first functional analog pin or pad, and keep disconnected an input or output of the second analog circuit from the first analog test bus, and when the IC is in a test mode, selectively connect the input or output of the first and second analog circuits to the first analog test bus to test the first and second analog circuits using the first analog test bus.

A test and measurement instrument includes one or more channels to receive a signal under test, each channel comprising an input port, a filter, and a sampler, at least one analog-to-digital converter (ADC), the at least one ADC having two pipes connected to the sampler of one of the one or more channels, the at least one ADC to produce digital samples of the signal at a sample rate, and one or more processors configured to execute code that causes the one more processors to acquire a spectrum of the digital samples for each pipe in the at least one ADC, and use the spectrums of the digital samples for each pipe in the at least one ADC to reconstruct the spectrum of the signal under test. A method of operating a test and measurement instrument, and a method a method of calibrating a test and measurement instrument is included.