Pulse Generator for TDR

Thread Starter


Joined Sep 30, 2023
I have designed a Circuit to send a pulse down a coaxial cable for a cable fault detector, is someone able to have a look at this circuit and provide feeback, anything I should change? and also will it work, many thanks, still new to this.



Joined Aug 1, 2013
What kind of "cable fault" are you trying to detect, and how will you detect it? Are you looking at the timing of reflections with a scope?


Thread Starter


Joined Sep 30, 2023
I would question avfew thing,
why have you connected 5v to ground !
Where is the power connection for the chip
Where is the decoupling
Hi, am still new, have moved the pwr, if you wouldnt mind scribbling over this screenshot just to point out what I need to do to get this working, many thanks. still very new to this.



Joined Mar 30, 2015
am still new
Putting an LED across the 5V supply isn't going to work.

EDIT: Neither is having the input to the oscillator connected to 5V.

You have ignored advice from multiple sources point out that trying to have a 50 ohm output impedance is better than what you're doing. 50 ohms is close to the characteristic impedance of many RG type cables.

Since you're a newbie, you should study schematics drawn by people who knew what they were doing. Pointing ground every which way isn't a good practice. Some schematic editors use an up arrow symbol for positive power supply voltages and a down arrow for negative. Drawing ground up could get confused with power. People/editors who use arrows for power symbols don't usually use a down arrow for ground:

You should print to PDF to get rid of those meaningless, annoying colors. The pros have gotten by with monochrome for a long, long time.
Last edited: