Op amps find use in second-order filters and instrumentation amplifiers. In part 3 of this series, we described using the op amp to build some single-pole filters. Q: How do we build higher-order filters? A: Figure 1 shows one approach to a low-pass filter using the Sallen-Key topology. With two capacitors, it’s a second-order filter. […]
How to choose analog-signal-chain components: part 3
Use op amps, resistors, and capacitors to build high-pass, low-pass, and bandpass filters. In part 1 of this series, we looked at a noisy signal and discussed why it might be better to use an analog filter instead of a digital filter. Then, in part 2, we looked at the operational amplifier (op amp) and […]
How to choose analog-signal-chain components: part 2
Signal conditioning can prepare a sensor’s output for digitization. In part 1 of this series, we looked at a typical analog signal chain that you can use in conjunction with analog-to-digital converters (ADCs) or digital-to-analog converters (DACs). A key building block of the analog signal chain is the operational amplifier (op amp), shown in its […]
How to choose analog-signal-chain components: part 1
Signal conditioning can prepare a sensor’s output for digitization. In a previous series, we looked at the analog-to-digital converter (ADCs) and sources of error that occur within the device. Of course, errors can creep in upstream of the ADC along the analog signal chain as the signal to be digitized is acquired and conditioned. Q: […]
Understanding ADC specs and architectures: part 5
ENOB describes an analog-to-digital converter’s performance with respect to total noise and distortion. In the earlier parts of this series on analog-to-digital converters (ADCs), we looked at the basics (part 1); gain error, offset error, and differential nonlinearity (part 2); and integral nonlinearity (part 3); and then we looked at some ADC topologies and introduced […]
Understanding ADC specs and architectures: part 4
The AC performance of an analog-to-digital converter depends on its architecture. In part 3 of this series, we discussed the integral nonlinearity (INL) error of an analog-to-digital converter (ADC), noting that gain, offset, and INL error all contribute to the total unadjusted error. This metric provides an overall view of an ADC’s DC performance. Q: What about the AC […]
Understanding ADC specs and architectures: part 3
Integral nonlinearity tracks the cumulative effects of an ADC’s differential nonlinearity. In part 2 of this series, we discussed several sources of error in an analog-to-digital converter (ADC), including gain, offset, missing-code error, and differential nonlinearity (DNL). We concluded with an illustration of a waveform with varying levels of DNL superimposed on the staircase representing […]
Understanding ADC specs and architectures: part 2
Specifications such as gain error, offset error, and differential nonlinearity help define an analog-to-digital converter’s performance. In part 1 of this series, we discussed an ideal analog-to-digital converter (ADC), noting that it would have infinite resolution and bandwidth. Then we looked at the real world of practical inverters and how their resolution, expressed in a […]
Understanding ADC specs and architectures: part 1
Analog-to-digital converters are the heart of most test equipment, setting the stage for the digital processing of analog signals. Several posts over the past year or so have involved digital signal processing. For example, we have covered the fast Fourier transform (FFT), the inverse FFT, and discrete convolution. To perform these operations on real-world signals, […]
How to use convolution to implement filters: part 4
A windowed sinc function can implement a low-pass filter, and a two-dimensional convolutional filter can blur or sharpen images. In part 3 of this series, we introduced a low-pass filter based on the Sinc function and described the need for windowing to compensate for sampling and truncation. Q: How can we apply this filter? A: […]
