55 votes
Accepted

Why is the bitrate of infrared smaller than the bitrate of WiFi?

The premise is false. Infrared communication can be much higher bandwidth than wifi; just look at modern fiber-optic communications. It looks like you're really asking why wifi is faster than the ...
Hearth's user avatar
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33 votes
Accepted

Frequencies are inherently positive physical quantity.... what does it mean?

Frequency is how many times something happens every second. So it can't be "minus 5 times a second". However when you do actual signal processing, you'll see negative frequency on the graph ...
TQQQ's user avatar
  • 1,258
26 votes
Accepted

If capacitors are frequency-dependent resistors, then what are inductors?

If you consider capacitors as frequency dependent resistors, then by same logic, inductors are frequency dependent resistors too. The difference is that they work opposite based on frequency. At DC, ...
Justme's user avatar
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23 votes

Is there any way to measure sound intensity in decibels without using a microphone?

If your customers aren't electrical engineers, how would they tell a small microphone on your main circuit board from say an oscillator, opamp, or voltage regulator? So any customer that only buys ...
Constantine A. B.'s user avatar
20 votes

If capacitors are frequency-dependent resistors, then what are inductors?

To the extent that capacitors are frequency-dependent resistors, so are inductors -- just with the opposite frequency dependence. But be careful with that metaphor -- it's sort of like saying that you ...
TimWescott's user avatar
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16 votes

How can prevent the source voltage from dropping when using a 555 timer

The root problem is not external inductance, it is an internal design flaw. The original bipolar 555 design is notorious for output stage cross-conduction. This is a condition where both output ...
AnalogKid's user avatar
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15 votes

Why is the bitrate of infrared smaller than the bitrate of WiFi?

Even free-space IR connections can be quicker than you think - or at least they were 20 years ago. Consider some of the IrDA standards for line-of-sight IR. They can get into the hundreds of Mbit or ...
Chris H's user avatar
  • 2,581
12 votes

Is there any way to measure sound intensity in decibels without using a microphone?

You need to improve the definition of your problem. Privacy Does that mean any talking is unintelligible? The fact that some sounds can be heard, at a specific time, even if they are unintelligible as ...
Neil_UK's user avatar
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9 votes
Accepted

How are different GPIO frequency modes implemented?

Mostly, the slew rate for GPIOs is increased by adding more drivers in parallel like the one shown below. I have shown above an image of a GPIO that has 2 drivers. Each has an independent enable as ...
sai's user avatar
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9 votes

Is there any way to measure sound intensity in decibels without using a microphone?

Any device or transducer that can convert sound to electrical signal is by definition a microphone. Even capacitors can exhibit microphonics and can ruin your signal by converting audio or mechanical ...
Justme's user avatar
  • 143k
9 votes

Frequencies are inherently positive physical quantity.... what does it mean?

Frequency is related to time. Time in systems is only positive. For theoretical purposes you can consider time to be negative, but in the real world time is always positive
Voltage Spike's user avatar
  • 81.1k
9 votes

BJT as current buffer for op amp

I'm sorry but pursuing that approach is probably not going to work for two reasons: - DC offsets will cause problems with an inductive load (can be solved) Not enough supply voltage to get 5 volts p-...
Andy aka's user avatar
  • 451k
8 votes

Why is the bitrate of infrared smaller than the bitrate of WiFi?

You are comparing apples to oranges, when considering the bitrate of the communications channel you not only need to consider the frequency of the medium that's traveling in but also the bandwidth (...
Voltage Spike's user avatar
  • 81.1k
8 votes

Frequencies are inherently positive physical quantity.... what does it mean?

Consider a spinning disc. It can rotate clockwise or counter-clockwise. Clockwise angles \$\theta\$ are considered negative while counter-clockwise angles positive, The angular velocity \$\omega\$ is ...
RussellH's user avatar
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7 votes
Accepted

How can prevent the source voltage from dropping when using a 555 timer

The problem is most likely the lack of a power supply decoupling capacitor. When using a breadboard to prototype analog circuits I always put a 10uF capacitor on the supply rail.
earl's user avatar
  • 1,105
6 votes
Accepted

Does the capacitance of a Schottky diode depend on switching frequency?

The supplier has to measure capacitance using an oscillator and, that oscillator has to use a certain frequency. Given that a nominal value of 30 pF at 1 MHz implies a capacitive reactance of 5305 Ω, ...
Andy aka's user avatar
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6 votes
Accepted

Flip Flop as frequency divider precision

The chances are that the flipflop is responding to very short glitches on your power supply. Modern ICs can respond to clock inputs measured in nanoseconds. A momentary spike on your supply could be ...
Simon B's user avatar
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6 votes

Flip Flop as frequency divider precision

You have not provided enough information - like a schematic - to be able to answer with more certainty. But, the outputs of the 4N25 opto is not the nice, sharp edge that's indicated on your 'scope ...
SteveSh's user avatar
  • 10.5k
6 votes

Does locking a CPU frequency to a higher state (even OC) have any downsides?

... at idle, 4.1 GHz @ 1.35V and 1.6 GHz @ 0.6V uses roughly the same amount power. This doesn't make sense to me. The power consumption of a CPU can be thought as a sum of static and dynamic ...
Rohat Kılıç's user avatar
6 votes

Why does an AC Voltage reading on a DMM decrease as the frequency is increased?

The oscilliscope is designed to display a wide range of frequencies accurately - from DC to 50 MHz or more, while a common DMM will usually only cover a much smaller frequency range - mine shows the ...
Peter Bennett's user avatar
6 votes

Why does an AC Voltage reading on a DMM decrease as the frequency is increased?

On a cheap meter the signal is AC-coupled, then rectified using a precision rectifier and then low-pass filtered yielding an average voltage, which is then (for display) (effectively) multiplied by ~1....
Spehro Pefhany's user avatar
6 votes

BJT as current buffer for op amp

Is there any method which can be used to achieve the 10-20Khz 0-5V sine wave Using 5V supply? A class D amplifier IC will do it, but it won't be exactly a 0-5V sine wave due to resistive drops in ...
Kuba hasn't forgotten Monica's user avatar
5 votes
Accepted

unfamiliar notch filter configuration

This is one of those interesting circuits. The upper amplfier, U1, is a differential amplifier. When redrawn, as below, the differential amplifier topology becomes clear. The Lower amplfier, U2, is a ...
qrk's user avatar
  • 9,149
5 votes

What is the maximum frequency for a diode if a superimposed AC sine wave on DC pass through it, and the diode stays always ON due to DC?

Unless the diode is used as a switching device, the frequency doesn't matter, at least for the range you are working with. If the amplitude of the AC is high enough to "turn off" the diode ...
Rohat Kılıç's user avatar
5 votes

What is the maximum frequency for a diode if a superimposed AC sine wave on DC pass through it, and the diode stays always ON due to DC?

A diode always in forward bias, has voltage drop and incremental resistance corresponding to instantaneous current. This is true regardless of type, and applies from DC, up to frequencies where ...
Tim Williams's user avatar
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4 votes
Accepted

LoRa - Frequency Shift Chirp Modulation - chips in a symbol

The Shannon–Hartley theorem gives the channel capacity as: $$C = BW.log_2(1+\frac{S}{N})$$ When \$S \approx N\$ (signal level is close to noise level), this means that \$C \approx BW\$, in other words,...
jcaron's user avatar
  • 1,974
4 votes

Counter showed 50Hz when I put it across my body. Why?

Because your body acts like the plate of a capacitor and picks up residual electric fields from the AC wiring in your house and, the meter detects these as 50 Hz.
Andy aka's user avatar
  • 451k
4 votes

Does the capacitance of a Schottky diode depend on switching frequency?

Generally it is not dependent, and the info is provided merely for reference. There may be devices which do exhibit frequency dependence. Which is to say, losses, or diffusion effects, or other ...
Tim Williams's user avatar
  • 31.7k
4 votes

Flip Flop as frequency divider precision

A flip-flop is never imprecise. Assuming suitable inputs, it does exactly what it’s told so one can assume the results are real. Here, without a Schmitt trigger, the results may well be hard to ...
Kuba hasn't forgotten Monica's user avatar
4 votes
Accepted

What is the resonant frequency?

As you've already said, the resonant frequency is the frequency at which the reactance of the circuit is zero. This means that you have to derive a formula for the impedance of the entire circuit and ...
Jonathan S.'s user avatar
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