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50 ohm impedance match

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scorpyann

scorpyann

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50 ohm impedance

does anybody know what is the 50 ohm impedance and how do we know when to use 50 ohm impedance on the pcb board? pls help me
 

50 ohm trace width

You will only use 50 Ohm traces if the load and source requires that. If you coupling signals between amplifiers that are both 50 Ohm I/O then you will use a 50 Ohm trace to prevent reflections in the line.
 

50 ohm impedance matching

i'm designing loadboard which will be used to test the highspeed device, do i need to control the impedance?
 

50 ohm impedance trace width

I am not sure what you mean by high-speed. (1GB/s or 20GB/s?)

Look at the video's by national on high speed data transfer where Dr. Howard Johnson points out things to look for in high-speed pcb layout.

**broken link removed**
 

trace width 50 ohms

the highspeed device is where the rise/fall time of the device is very small, around 2-3ns. that's mean, the freq is quite big, around 117Mhz (formula: freq=0.35/rise time)
 

trace width for line impedance 50ohm

High-speed is a relative expression. For me a fast risetime is less than 150pS.

At 117MHz over short distances (<< 1/4 λ) pcb trace thickness won't be critical
 

current to drive 50 ohm

yes, the trace thickness won't be critical, how about the impedance match? do i need to sandwich each signal layer with gnd and set the layer to 50 ohm?
 

how to match 27 ohms to 50 ohms impedance

Sandwiching signal layers between gnd's is not always a good idea. It is not possible to give you answers on a general question like you ask without knowing more details about your circuit. A lot will depend on your circuit. What do you mean by setting the layer to 50 Ohm?

Take the time and look at the Johnson videos as it may answer some of your questions.
 

50 ohms control impedance in 2 layer board

hello

Maintaing 50 ohm impedence is compulsary. why 50 ohms?

Because IC s can drive 50 ohms impedence. you can achive by maintaing

the stack-up of the board, controling the core and prepeg thickness and adding

planes will give u the 50 ohm impedence.
 

why 50 ohm impedance

The main reason for working with 50 or 75 Ohm impedances will be that it makes connecting to most test equipment for measurements easy.
 

why 50 ohm is used

yes, for high speed signals, it's recommended to control 50 ohm impedance
 

how to pcb 50 ohm impedance

yes, i'm thinking of it also
 

pcb 50 ohm impedance test

check this may be useful
 
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pcb 50ohm width

it is mechanical ,relate to fabrication
1)if we use more than 50ohm trace,then fabrication some waht difficult.because we can not fabricate tarace width is less than 3 mills.it is minimum.
2)if we use less than 50 ohm then ,the trace width is more.it is not better for high density boards.

so mostly 50 ohm trace prefered.

Trace impeadance is dependence geometry of the trace.

but video application 75 impeadance is prefer.

plz inform if anything is wrong.

Added after 31 minutes:

electrical:-
1)every logic family have diffrent output impeadance.to satisfy all the logic families 50 ohm imoeadance is uesd.
2)if use more than high impeadance trace ,more current is require to drive the trace.
3)if use less than 50 ohm impeadance used ,automatically current density increase by ohm's law.

so both the cases probelem .
so mostly 50 ohms prefer.
 

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