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1500 questions
28
votes
5 answers
Is there anything I should watch out for with cheap "Arduino" copies?
There's a plethora of cheap Arduino copies on eBay and similar sites, usually originating from the far east, that can be had for a significant chunk less than the official boards, especially if you're buying more than one.
Aside from the moral…
berry120
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28
votes
3 answers
Why pull base of BJT switch?
I often notice usage pull resistor for base of bipolar transistor, e.g. \$R2\$ here:
Why it's used? I understand pull resistors for FETs, because of gate's high impedance an EMI can easy switch it. But BJT need base's current to open and, I think,…
user54579
28
votes
2 answers
What is the difference between "reverse stand off voltage" and "breakdown voltage" on a TVS?
On a transient voltage suppressor, let's take a unidirectional Fairchild P6KE11A for example, what is the main difference between reverse stand off voltage (\$V_{RWM}\$) and breakdown voltage (\$V_{BR}\$) as shown on the chart on page 2?
In my…
JYelton
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28
votes
7 answers
Why are integrated circuits powered by low voltage and high current?
I've heard that a typical graphics card uses around 100 A of current and only 1 V of voltage. Is there a specific reason why not to use the other way around, so high voltage and low amp? Usually high current leads to high losses, that's why power…
Maxim
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28
votes
6 answers
Is it possible to make illegal clones of an Intel Core i7?
The reason I'm asking is that on http://alibaba.com you can find prices for the Core i7 as low as $20, minimum quantity 1. This looks like impossibly low for a genuine Intel, but then I also can't believe you can clone this kind of CPU. What's the…
Federico Russo
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28
votes
5 answers
Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?
Background
In EEVBlog #1116, Dave discusses a method to remove power supply ripple, and goes on to show (see 5:17 to 6:15) that you cannot count on linear regulators to remove your input ripple. He gave a concrete example in the lab: at 10 kHz input…
anrieff
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28
votes
5 answers
Due to overcurrent, shouldn't I be extremely cautious when setting an I/O pin as Output?
The question can be applied to any microcontroller with I/O capabilities, but I’m currently working with the popular ATmega328p. Consider the following circuit: A simple SPST Normally Open switch with a 10k pull-up resistor and a ceramic capacitor…
Julian Zatloukal
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28
votes
6 answers
Why wasn't interlaced CRT scanning done back and forth?
I was studying the scanning of old CRT screens and the interlacing strategy for video, and I started wondering something.
The raster scan process went top to bottom on odd lines, then back to top to raster the even lines. There is therefore a…
Stefano Borini
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28
votes
4 answers
Can you actually break an FPGA by programming it wrong?
Can you actually break an FPGA by programming it incorrectly?
I'm a software guy really. It's no secret that if your software is wrong, you could destroy all sorts of important data, and perhaps even crash the whole machine. But it's really…
MathematicalOrchid
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28
votes
5 answers
Why are GND pads often only connected by four traces?
I have seen this everywhere but cannot figure out why it would make sense to essentially compromise the quality of the ground connection. Is this done for visual reasons?
Here is an example:
Wi_Zeus
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28
votes
3 answers
FPGA programming, where to begin
I'm a software developer (C, C++, objective-c, java ...) and I am interested in learning to program FPGAs. Now the question may appear simple to you but please do take time to help me on this one as I'm kind of stuck right now. My company has asked…
Anila
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28
votes
6 answers
Frequency dependence of electrolytic capacitors
It's said that electrolytic capacitors behave as inductors at high frequencies, which is why we put small ceramic caps in parallel with them:
Electrolytic, paper, or plastic film
capacitors are a poor choice for
decoupling at high frequencies;…
endolith
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28
votes
1 answer
Who said, "all sensors are temperature sensors, but some are better than others"?
One of my favorite electrical quotes goes something like "all sensors are temperature sensors, but some are better than others". Unfortunately, I don't remember where I read this. What is the origin of the quote?
Dan Kowalczyk
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28
votes
3 answers
Why solder mask are not applied to RF PCBs
I've gone through some of the RF PCB designs. In which solder masking on the traces are not present. Like this one
Is there a specific reason or performance issue to remove that?
Abhishek Parikh
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28
votes
3 answers
What makes one microphone better than another, and how do I make my own?
I am curious about microphones and have a few questions.
What is the key component in them which makes one better than another?
What does it take to build a high quality microphone on my
own? I'm looking to purchase a good microphone, and was…
capcom
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