Some analog applications are very noise sensitive such as medical equipment, communications equipment, instrumentation, or test and measurement equipment. Elimination of all potential noise sources in a circuit may be necessary, including conducted, radiated, and thermal noise. One possible source of conducted noise can be found in the power supply bus. Eliminating this noise […]
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Transimpedance amplifier role in current to voltage conversion
A transimpedance amplifier (TIA) converts current to voltage. Transimpedance amplifiers can be used to process the current output of photodiodes, pressure transducers, accelerometers, and other types of sensors to a voltage formatted as a useable signal output. TIAs provide simple linear signal processing using an operational amplifier and a resistor for dissipating current. Figure 1 […]
Ground rules: earth, chassis, and signal ground
In analog design, the relationship of a signal to ground is of fundamental concern (and can create issues in digital designs, too.) However, “ground” as a concept can be confusing as it relates to three different situations: chassis ground, signal ground, or earth ground. All three indicate connecting to a point of (theoretically) zero voltage, […]
What are the noisiest resistors?
Noise in circuits is always going to exist in one way or another. For those working with or designing electronics, noise can ride the working signal and can obscure small signals altogether. Barring any other sources of noise, if very low-level signals are important, you may want to look at your resistors. Resistors are inherently […]
Top analog threads on EDAboard.com – June
(editor’s note: Intrigued by the problem? Have a question or optional solution? Then click the “Read more” link and follow the conversation on EDAboard.com or log in to EDAboard and participate in the analog IC forum thread.) Query about VU meters – I bought one today and tried it just now I am probably using […]
Interfacing and using bridge sensors
Sensors such as strain gauges, pressure gauges and some magnetic sensors are often bridge devices. They can be full or half bridge although the bridges are usually made of multiple devices connected together, with MEMS sensors being an exception. So, in the case of a strain gauge, a half bridge would be made with one […]
Signal line and supply filtering
There are many reasons for needing to filter power supply or signal line. Power supply lines from a switching regulator may be too noisy for sensitive analog circuitry. Signal or power supply lines may pick up interference either from the rest of the system circuitry or from external devices. With signal lines the problem of […]
Troubleshooting analog circuits
While you may need to troubleshoot a circuit that used to work and now doesn’t, the emphasis here is how to troubleshoot a design when you have your first PCB made. While you may be fortunate and everything works perfectly first time, there is often a need for some troubleshooting with a new design. The […]
When inductors self resonate
Inductors only behave like inductors below because of what’s called their self resonant frequency. And the self resonant frequency arises because the equivalent circuit of real-world inductors isn’t strictly inductive. There are parasitic elements that come into play. To understand why, look at the equivalent circuit for an inductor. An inductor can be comprised of […]
Level shifting digital logic signals
In the past digital systems were 5V and analog ones +/-15V or +/-12V. Nowadays analog systems are more likely to be single supply 5V, 3.3V or lower and digital circuitry is likely to be 3.3V, 2.5V, 1.8V, 1.2V or something in between. You might also have LVDS, DDR or other differential or single ended standards […]
