Chapter 11: DAC Testing

11.1.1 Intrinsic Parameters versus Transmission Parameters

In Chapter 8, "Analog Channel Testing," and Chapter 9, "Sampled Channel Testing," we discussed common channel parameters such as gain, gain tracking, signal-to-noise ratio, and signal to total harmonic distortion. These parameters are called transmission parameters, or performance parameters, since they describe the effect of the analog or sampled channel on the quality of transmitted signals such as voice or modulated data. In both analog and sampled channels, transmission parameters are determined by the quality of all the channel's subcircuits. For example, the signal-to-noise ratio of a DAC channel might be determined by the quality of a low-pass reconstruction filter, an output buffer amplifier, and of course the DAC itself.

In this chapter, we will focus on the so-called intrinsic parameters of DACs, such as absolute error, integral nonlinearity (INL) and differential nonlinearity (DNL). Intrinsic parameters are those parameters that are intrinsic to the circuit itself. They are not dependent on the nature of the test stimulus. For example, the difference between the actual DC voltage level measured at a DAC's output and the ideal voltage level is called absolute voltage error. Absolute voltage error can be measured at each digital code, resulting in a set of intrinsic voltage error values. Since these errors are determined purely by the quality of the DAC circuitry and not by the nature of the transmitted signal, absolute voltage error is considered to be an intrinsic parameter. Transmission parameters,...