# no ideal pulse

#### aragon1971

Joined Apr 7, 2008
46
hi friends

why in digital pulse there rise time, fall time .. etc and the delay time

Joined Mar 10, 2018
4,057
To move electrons takes time and energy, they have mass.

Regards, Dana.

#### BobTPH

Joined Jun 5, 2013
2,538
No signal can travel faster than the speed of light, to give another reason.

But the real practical limit comes from the fact that there is stray resistance, capacitance, and inductance in every circuit.

Bob

#### crutschow

Joined Mar 14, 2008
25,396
Nothing in the real world is ideal.

#### OBW0549

Joined Mar 2, 2015
3,546
The only way you could ever achieve an "ideal pulse" would be if there was no such thing as capacitance or inductance.

#### nsaspook

Joined Aug 27, 2009
7,587
The only way you could ever achieve an "ideal pulse" would be if there was no such thing as capacitance or inductance.
+1
That would also mean a infinite speed for light (speed of causality) with the electrical length for all connections being zero. Something that only happens in simulators or circuit theory math problems.

#### Delta prime

Joined Nov 15, 2019
490
Electric currents, like current electricity, means the moving of electrical energy from one place to another via the moving of electrons. We can manipulate electrons to give a particular result. A digital pulse is a waveform like any way form it must be defined to make sense. The digital pulse you provided is a visual representation and the product of manipulating electrons define by its rise time, fall time, bandwidth, amplitude xcetera, and it's proven mathematically. I speak in generalities. And now I am at a high potential for "Cannon fodder".

#### nsaspook

Joined Aug 27, 2009
7,587
Electric currents, like current electricity, means the moving of electrical energy from one place to another via the moving of electrons. We can manipulate electrons to give a particular result. A digital pulse is a waveform like any way form it must be defined to make sense. The digital pulse you provided is a visual representation and the product of manipulating electrons define by its rise time, fall time, bandwidth, amplitude xcetera, and it's proven mathematically. I speak in generalities. And now I am at a high potential for "Cannon fodder".
Well maybe, sorta. Current electricity (moving charge) has very little energy in most electrical transmission circuits and the electrical energy that provided the KE (moving charge) to electrical charge is generally transformed to 'heat'. The pulse we see in a normal digital signal is a representative (with possible reflection patterns) of the EM field(s) that actually transports electrical energy using free charge as the pathway/wave-guide. The fields and charges work as a system in current electricity.

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#### Delta prime

Joined Nov 15, 2019
490
hi friends

why in digital pulse there rise time, fall time .. etc and the delay time
The ninth thread I'm hoping was appropriate for the question?My apologies if I may have caused confusion. I do very much enjoy reading the answers you provide nsaspook! And I am blown away that you even quoted me, and by the way I'll take
Well maybe, sorta
From someone of such high caliber.

#### MrAl

Joined Jun 17, 2014
7,803
hi friends

why in digital pulse there rise time, fall time .. etc and the delay time

View attachment 197528
Inductance and capacitance and resistance are inherent in most circuits.
Inductance prevents the current from rising or falling instantaneously.
Capacitance prevents the voltage from rising or falling instantaneously.
Inductance and capacitance together resonate and cause the ringing.
The damping of the ringing is caused by the resistance.
Delay time is often caused by stored charge that has to be removed or added before the drive energy can start to change the current and voltage that make up the pulse shape.
That is more or less the analysis in time.
For the analysis in frequency we would say that the overshoot and left to right tilt is due to low frequency attenuation which usually is the cause of the droop.

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