Early semiconductor devices were based on germanium, although there were others around such as selenium used in rectifiers. Germanium doesn’t need to be as pure as silicon for making devices but has higher leakage and is not so good at high temperatures so silicon has taken over and is the mainstay of current electronics. However, […]
FAQ
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 […]
Variable gain amplifiers
It is not uncommon to need an adjustable gain in an analog signal processing chain. If the adjustment is manual then it is pretty straightforward — you can use a potentiometer. When you need the adjustment under digital control then it becomes more complicated. If you need a digitally adjustable instrumentation amplifier then there are […]
Calculating and comparing amplifier noise
I was recently presented with the problem of comparing the noise of two alternative designs that were presented to me. Normally that wouldn’t take much sorting out – a few minutes with a SPICE simulator and you would have the answer. That depends on having reliable SPICE models. The first thing I do when embarking […]
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 […]
Choosing, using and designing oscillators
Most electronics today have oscillators in them. Digital circuitry needs a clock. Radio frequency signals require an oscillator or clock. Some analog circuitry also needs a clock or oscillating signal source. If you are using a microcontroller then it might have a built-in clock, although it may not be accurate enough, depending on your application, […]
Amplifier Theory: Design & Troubleshooting, Part 1
By unclejed613, “Well-Known Member” on Electro-Tech-Online. No matter how “digital” things get in modern consumer electronics, when it all comes down to it, after all of the digital magic is done, air must be moved for you to hear the results. An analog voltage and current must be applied to some type of device that displaces air. […]
How to reduce noise in an electrical circuit
“Noise” can mean different things to different people. In general it is associated with something unwanted. It could be acoustic noise – background noise. In electronic terms it will generally be an unwanted electrical signal. That may be random or systematic. Either way, it would be a nuisance if the level is high enough to […]
How not to design analog filters
I thought I would share some of the crimes against filters that I have seen people commit over the years. 2+2=4? So, you have designed a 2 pole Butterworth filter for example and want a 4 pole one so you put two of them together. You have a four pole filter? Yes, but not a […]
Using LTspice for power supply design
Simulation using a SPICE simulator (Simulation Program with Integrated Circuit Emphasis) is handy for checking out designs before building them as well as helping to understand designs and circuit problems. You can experiment without blowing anything up! LTspice from Linear Technology is particularly useful as it is free and available to download from their web […]
