Impedance Matching - why we match output and input impedance
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- Опубликовано: 28 июн 2024
- / pawelspychalski
Have you ever wondered why a cable has impedance? And what impedance really is? And why we should match the output impedance of one device with an input impedance of the other? Those are all very good questions. To some of them, I will give an answer: in layman terms. First of all, impedance is a sum of all resistances: static and frequency dependant coming from capacitance, inductance, and reactance.
Second of all, the voltage cannot exist without current. By changing the input/output impedance ratio, we change how much voltage comparing to current flow from one device to the other. And guess what... the most power is transferred when that ratio is 1:1 - input impedance is matched to output impedance. Half of the voltage might be lost in a voltage divider, but still, power is transferred in a most efficient way.
On top of that, when working with high frequencies, when the impedance is not matched, reflections as appearing and they take away some of the signals as well. It's just like a reflection in a glass of water. Air and water and "transparent" but since they have different densities, some of the light is reflected at the border between them.
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I have a second video on this topic that is half the length and I think covers the topic slightly better. Here is the link ruclips.net/video/9QzujzJCnTY/видео.html
Thank you for the refraction analogy! That's what made impedance matching click for me
Coax cables have a impedance designation for the impedance to remain the same regardless of length. This is achieved by having the core and shield of the cable at a specific distance and the insulation having a specific value, giving a capacitance that increases with the length of cable.
It doesn't stay the same if there's a mismatch
Very practical explanation.
Glad you think so!
Another place where impedance matching comes into play, (in a low frequency application) occurs when connecting a solar panel to a battery. You want maximum power transfer from the solar panel to the battery. A good charge controller matches the impedance of the solar panel to th battery. A good impedance match results in more power being transferred faster to the battery.
So I am using your video for my presentation :)
what is the additional instrument to measure the output impedance for 5.8ghz fpv video transmitter? .. since the 5.8fgz antenna said its impedance is 50ohm...but the signal result not as expected....from this video i learn the problem might be the mismatch impedance between 5.8ghz VTX with Antenna...
Hi, Regarding high frequency circuits the load will be CMOS type and will have high input impedance in the range of Meg ohm. How do we match this source and characteristic impedance which is of 50 ohm? Thanks in advance !
what is the ohm of electrical cable ?
it depends on mental , thickness and Legnth of wire .
but when we talk about 50 ohm cable why it's always 50 ohm no matter how long or thick it is , like cable tv wire ?
It's the impedance, not resistance per meter
@@PSAfterHours so what makes diffrence between 25 ohm 50 ohm and 70 ohm cable ?
The impedance :) Read this www.bluejeanscable.com/articles/impedance.htm but long story short: if you have 50Ohm output and 50 ohm input impedance, you should use 50Ohm cable to connect them
Thanks
love the russian accent and information is perfect also the examples and analogy... thanks sir
For the record, I'm not russian
Just in your Mongolian head ?
That's Polish.
Clear as mud! But seriously knowing that there is a difference between amp to signal matching and standard power transfer and cable transmission really does help.
I think there is also the Case when You want a Lot of Current. Like a Short basically... :D I think, it is the Opposite of Voltage Matching... High Output-Impedance and very low Input Impedance will give You a Lot of Current (but not much Voltage.. ) ...
Is it possible to match or tune impedance with potentiometer??
Yes, at DC. At high frequency a potentiometer won't be only resistive. You have to be careful to ensure the potentiometer's wiper can handle the current.
Yes, All My Coax Cables Are 75 Ohms
(and everything works OK!)
more higer the diferance in impeadance between 2 points than
more watts volume goes as AC signal but less Current
& lo impeadance signal goes more efficient to High impedance
but…
gues’s steady high speed back and forth realation
what is current ? is there something new about it .
And yet voltage doesn’t get “output”
Arnaque a base de sa
"You cannot have the voltage without the current" - incorrect.
Depends how you look at it. If you measure voltage between 2 points and there is a potential difference, small (very small) current will flow through the measureing device. Ergo, in practical terms, when you measure the voltage, small current flows
@@PSAfterHours having three batteries, connect battery A+ to B-, B+ to C- and C+ to A-. Now the funny thing happens, no matter which two points you measure between in this triangle you will measure 0 volts but lots of current is flowing 🙂
@@BaldurNorddahl It's not actually 0, it's just so small you can't measure it.