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1500 questions
37
votes
9 answers
Why do capacitors lose capacitance in series?
Unlike rechargeable batteries, capacitors have a lower capacitance in series. Why is this and if I charge each cap separately and then put them in series, will it still be a lower capacitance?
skyler
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37
votes
4 answers
If we could start our electrical grid from scratch with today's technology, which would be the most efficient choice? AC or DC?
Lately, I’ve been reading about the many advantages of HVDC transmission systems for long distance transmission, undersea links, and others. The historical reason of why AC was picked over DC was mostly due to the invention of the transformer, which…
Jota
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37
votes
10 answers
Is an Arduino Uno capable of running 24/7?
I'm curious as to the reliability and durability of the Arduino Uno.
Does anybody have experience in "killing" one due to excessive use?
If so, how long did it take for the board to fail?
nathangiesbrecht
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37
votes
6 answers
What is the purpose of a resistor in the feedback path of a unity gain buffer?
I often see unity-gain followers with a resistor in the feedback path. For an ideal op-amp, of course, there is no current into the input, and this resistor does nothing. What is its effect with a real op-amp, and how do I choose its value?
What…
nibot
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37
votes
2 answers
What kind of tape is used to hold together electronics during shipping?
Not so fast! This isn't that kind of tape (Kapton).
By holding electronics together, I mean to hold mechanical parts together for shipping such as flaps and other parts that can flop such as printers and scanners.
It's a very thick material that…
Zhro
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37
votes
3 answers
How to decide between a TVS or Zener diode for overvoltage protection?
I'll leave my specific circuit out of this for a more broad question:
What criteria does one use when deciding whether to use a Zener diode or a transient voltage suppressor, for overvoltage protection on a particular application? Also when would…
JYelton
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37
votes
1 answer
Why were germanium diodes so fast and germanium transistors so slow?
Germanium diodes were used for Radar during WW2. Germanium transistors appeared about a decade later. Most early transistors were only specified for audio use, like the OC71. The specified RF types like the OC44 were only good for a few MHz. Why…
Autistic
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37
votes
2 answers
What is this symbol: semicircles facing each other?
What does this symbol represent?
It was found on the circuit diagram for a TDS973A a board for which this was the only information I was able to find online.
faire
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37
votes
2 answers
Weird resistor with dots around it on the schematic
I was looking through the LTC4041 datasheet and saw this:
The 10mOhm resistor with the two nodes really close to it - is that a "special" resistor or something? Why have they drawn it like that?
AlfroJang80
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37
votes
2 answers
What is bit banging
I am new to microcontroller programming. I am using ATmega32-A controller and CodeVisionAVR compiler. I am using the waveform generator(AD9833) to generate a sinewave signal using SPI communication. I am able to generate the sinewave successfully.…
verendra
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37
votes
9 answers
What is the basic difference between AM and FM radio?
I want to know the basic/fundamental difference between AM and FM radio. Why nowadays FM radio has replaced AM and has become more popular?
user11832
37
votes
4 answers
What is the advantage of the inverting opamp circuit over non-inverting one?
Op amp circuits are designed to achieve a specific gain regardless of the differences between individual op amps. One very common circuit has a gain of -R2/R1. Here's a (corrected) schematic:
Another common configuration has a gain of R2/R1+1 and…
Dov
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37
votes
2 answers
What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?
For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the on-resistance would have to be deduced from the IDS…
endolith
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37
votes
2 answers
Selecting a MOSFET for driving load from logic
I'm looking to drive a magnetic door lock from an Arduino. I've found a question about driving a solenoid from an Arduino, which includes a circuit that looks perfect for this kind of situtation:
What I don't understand is how to select a MOSFET…
Polynomial
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37
votes
3 answers
Why do Arduinos ship w/ 16MHz crystal instead of 20MHz?
Why do Arduino boards ship w/ 16MHz crystal instead of 20MHz? They are spec'ed for operating at 20MHz, after all.
I guess there are a few advantages to running more slowly (lower power consumption, longer life), but I must be missing something.
Jellicle
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