What is a PCB?

One of the major concepts in electronics is the printed circuit board or PCB. It’s so fundamental that people often forget to explain what a PCB is. Electronics have come a long way. A journey that started with vacuum tubes and relays got its way into silicon and ICs. It became more prevalent in consumer goods. Therefore, there is always pressure to reduce the size and manufacturing costs of electronic products. This drove manufacturers to look for better solutions.

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Measuring PCB, Cable and Interconnect Impedance, Dielectric Constant, Velocity Factor, and Lengths

Controlled impedance printed circuit boards (PCBs) often include a measurement “coupon”, which typically includes sample traces, 6 inches long and constructed as part of the printed circuit board panel.  They are measured to assure the PCB stack-up and the accuracy of the PCB transmission lines. These coupons, as well as the actual PCB signal traces, interconnects and cables are typically measured using a Time Domain Reflectometer (TDR).  A TDR is generally a large, expensive instrument that includes a high-speed edge pulse and a sampling oscilloscope.

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Optimizing Power for Clocks and other Sensitive Applications


The topic of clock jitter performance seems to be a current focus of clock, ADC, and power supply manufacturers.  The reasoning is clear; clock jitter interferes with the performance of digital circuits including high speed ADCs.  High speed clocks can be quite sensitive to the “cleanliness” of the power they receive, though quantifying the relationship takes some effort.

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