57 votes

If a square wave has infinite bandwidth, how can we see it on an oscilloscope?

We can't. We see a bandlimited version. That's obvious for two reasons: perfect square signals cannot physically exist, for changing a voltage within 0 time would require an infinite amount of power ...
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41 votes
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Was the last mile copper wire not the limitation in dial-up internet service?

Is this...the same ...pair of copper wires that...was formerly used to provide dial-up internet service? Same wires, but those wires weren't put there for dial-up, they were put there for voice. And, ...
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  • 2,295
36 votes
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How am I getting 1 Gbps through a CAT3 cable?

100 feet is not extremely long; so, as Dave says, you've got lucky, and your Gigabit Ethernet hardware is just exceedingly robust. You have to realize that "Cat3" doesn't put an upper limit ...
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26 votes

If a square wave has infinite bandwidth, how can we see it on an oscilloscope?

You are correct that an ideal square wave needs an infinite bandwidth as it contains frequencies up to infinite frequencies. But this is theory, ideal square waves do not exist in the real world as ...
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  • 78.8k
20 votes

Why do FM radio signals occupy greater bandwidth than AM?

They need not, narrowband FM occupies the same bandwidth as AM, for the same audio bandwidth. Transmitted AM bandwidth is fixed at twice the audio bandwidth. However, wide deviation FM provides ...
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18 votes

If a square wave has infinite bandwidth, how can we see it on an oscilloscope?

The 'scope won't show a perfect squarewave and if you zoom in on the timebase you should be able to see the rising and falling edges with some slope on them. This will be most obvious on an analogue ...
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14 votes
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How do I find an ADC circuit's bandwidth experimentally?

The bandwidth is the frequency for which the output is down 3 dB. It it a function of the analog portion of your circuit and does not depend on the sample rate nor the Nyquist rate which are basically ...
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14 votes

How am I getting 1 Gbps through a CAT3 cable?

The Ethernet speed negotiation process takes into account the capabilities of the devices at each end of the connection, but not the cable between them. Essentially, this means that if you connect two ...
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13 votes

Why are USB devices slower than 480 MBit/s

This is a very old topic, but it has no answer yet. This is my attempt: Why are today's implementations not capable of streaming at 53 MB/s? The calculations are nearly fine, but you are ...
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11 votes

Why do OOK transmissions have bandwidth?

Only an ideal sine wave with constant amplitude and single frequency that runs for infinitely long in time has extremely narrow bandwidth of a single peak. Having any changes to the ideal sine wave ...
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10 votes

Why do OOK transmissions have bandwidth?

On-Off Keying (OOK) is equivalent to AM modulation of the carrier with the data bit-stream with a 100 % modulation index. As a result the entire spectrum of the bit stream is up-converted to the ...
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  • 2,906
10 votes

Is -3dB bandwidth defined for any type of transfer function?

Is -3dB bandwidth defined for any type of transfer function? Maybe you do not realize what -3dB actually means? -3 dB means that the amplitude of the voltage (current as well) has dropped by a factor ...
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10 votes
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Maximum Ethernet bandwidth through a slip ring

Maximum ethernet bandwidth is about maintaining the characteristic 100Ω (transmission line) impedance of the 10Gbe cable from device to device. As long as that can be done, you could use many ...
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9 votes
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How do manufacturers limit bandwidth in oscilloscopes?

You should realize that sample rate (1 GS/s) and Bandwidth (70 MHz) are different things!!! They are related in that a certain sample rate dictates the maximum bandwidth of the signals which can be ...
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  • 78.8k
9 votes

How am I getting 1 Gbps through a CAT3 cable?

Check the error counters on your attached equipment - managed switches generally keep a track of errors and collisions. It may be that this link is suffering errors, but at gigabit/s, it's still ...
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  • 618
8 votes

Transmission of a digital signal over a medium

Theoretically a square wave has infinite bandwidth but it still looks reasonably square even if the bandwidth is severely compromised. A square wave is "made from" a series of ever-increasing ...
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8 votes
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How to estimate the analog bandwidth?

If your scope's input amplifier has a frequency response of a first-order RC-filter, you can roughly estimate the bandwidth from the rise time: $$BW ≈ 0.35 / t_R$$ To clarify, bandwidth is defined ...
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8 votes
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Op-Amp Speed: Bandwidth vs Slew Rate

Here you have an answer via a graph which is present in the specification of the op-amp or you can calculate it. (example of LM324 https://www.onsemi.com/pdf/datasheet/lm324-d.pdf figure 7) LM324 is a ...
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8 votes
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Why are coaxial cables typically faster/longer than twisted pairs?

Why are coaxial cables typically faster/longer than twisted pairs? The truth lies in the motivation for making twisted-pair (TP) cables: - TP has closely magnetically coupled wires that naturally ...
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  • 385k
7 votes

Transmission of a digital signal over a medium

A digital signal is composed of a fundamental frequency and an infinite number of odd harmonics. This is how the nice clean and sharp edges of a digital signal is made. As in the image below, you ...
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7 votes

Op-amp dominant pole bandwidth

Op amps which use dominant pole compensation have a constant gain-bandwidth product. You've cited a 5Hz dominant pole, and the LM301A datasheet gives a typical open loop voltage gain of \$160\text{V}/\...
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7 votes
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What physical factor affects the antenna's bandwidth?

There are hundreds of different antennas so for my simple attempt at an answer I'll concentrate on the "dipole" and I'm not going to go into formulas too much. What physical factor affects the ...
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7 votes

How do I find an ADC circuit's bandwidth experimentally?

The plots below (taken from here) show why calculating ADC 'bandwidth' from peak sample values may be problematic. The plot on the right shows what happens when the sampling frequency is below the ...
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7 votes
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How can I know a signal's bandwidth before sampling?

It depends on the purpose of the sampling. If you need to sample a signal accurately - such as recording music where distortion is undesirable, you know the signal's bandwidth at the ADC, because you ...
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7 votes

Is bandwidth a parameter set in software by oscilloscope manufacturers?

Your colleague is basically right. Some scopes are software upgradeable. You can upgrade scope bandwidth or memory simply by purchasing a license. Which means same hardware can be sold with different ...
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6 votes
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Bandwidth of inverting and non-inverting op-amps

There is a simple answer: The bandwidth for the closed-loop gain is determined by the frequency where the LOOP GAIN is 0 dB. In your example circuits the loop gain is not the same - hence, the ...
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6 votes
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Op-amp dominant pole bandwidth

The dominant pole can be seen only in the open loop configuration. When you add negative feedback, gain is reduced and the BW is enhanced (for the closed loop system)
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6 votes
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Real rise time with oscilloscope and probe

No, the actual physics and formulas involved to get this absolutely right are not totally easy, but for gaussian response oscilloscopes (quick read about differences for flat response scopes: http://...
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6 votes

How do you use Gain Bandwidth Product to estimate bandwidth at different gains?

As @SpehroPefhany mentioned, we assume that the op amp has a constant gain-bandwidth product, GBWP. That is, \$\text{GBWP}=G \cdot B\$ for any gain G and bandwidth B. From the given information, we ...
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6 votes
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What is the purpose of the series of actions: amplification, band-pass, rectification, and low-pass?

The signals from the sensors were tiny, and needed to be amplified. Otherwise they would be lost in the noise in the rest of the system. When "interesting" things happen, neurons fire rapidly. ...
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