Electronics > Beginners

A noob question and Introduction

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DrRunCMD:
Hello the EEVBLOG forum!
I'm Chris Aka DrRunCMD (name on youtube).

About me:
Off the bat, I am from the UK, unemployed on sick due to diabetes complications etc. Live at home with parents, have kids and am nearly approaching 40! I am not an engineer or pro, I do small repairs and troubleshoot by logical thinking and some knowledge of electronics! I own a crap ton of circuit boards from TV power supplies to XBOX slim 360 boards. All used for spare parts or replacement boards.
I mainly do repairs of electronic consumer goods from TVs to PC's Servers etc for friends and family. Not as a paid job.
This DC LOAD project was inspiring to me, (thanks Dave), when he discussed the project on youtube. This was and is my first project where I designed the PCB and layout using EasyEDA online from scratch. I looked at the basics of how the DC LOAD circuit works which is simple, and began testing my own with variations of components. I remember having an issue the first time I built the basic circuit. I had a scope back then, the Rigol DS1054Z again was purchased after watching Dave's review lol. I only looked at ringing at the fet gate at turn on and switching anomalies etc. Then I had to sell the scope. Fell on bad times.
Im also a PC geek, server/network buff and do some old BASIC programming from time to time learnt from the ZX Spectrum. I own also a BBC Micro, very, very good working condition and I think is a relic and a treasure to own. Not thinking of selling it either. Depends on the price I suppose!
I own an EEVBLOG BM235 multimeter, and I love it! Can you buy the cables for the meter separately? I have lost mine at a previous job, now use crap ones!

I have a noob question..

I have made from scratch 2 DC LOAD circuits back when Dave was discussing as a project. The newest video I saw no #1247 was about signal propagation made me think of this project again. When driving two matched MOSFETs as a pair for power load/power-sharing, I wanted to ask, would the traces from the op-amp driving the fets have to be equal in length to each resistor then from resistor equal length to MOSFET?. The PCB's are 6x4cm, gold plated through-hole. I'm a noob, I told you. ( EXAMPLE ATTACHED IN PIC ).

Simply put: For driving MOSFETs with a control device (op-amp) for example, would gate control traces need to be at an equal matched length?

Not sure if this is signal propagation, integrity or even impedance, so my apologies if I'm wrong.
It just got me thinking about after watching the video.

Cheeky mention:
If anyone here has a personal, not using scope and would want to kindly donate one, I would be interested. Im in the UK.

Thanks, guys!
DrRunCMD

dazz:
I don't think trace length will matter in that application, if I got Dave right, it only matters for clock lines running in the MHz range. But I'm a complete noob too, so take that with a pinch of salt as I might be missing something

Hope things get better for you in the near future, Chris

magic:

--- Quote from: DrRunCMD on September 26, 2019, 10:53:49 pm ---When driving two matched MOSFETs as a pair for power load/power-sharing, I wanted to ask, would the traces from the op-amp driving the fets have to be equal in length to each resistor then from resistor equal length to MOSFET?

--- End quote ---
Propagation speed is some 20~30cm/ns. 2cm mismatch is 0.1ns difference. Not a problem for a circuit with a few MHz bandwidth.
Now, if you mismatch them by 2km... that could make a difference ;)

MosherIV:
Hi, welcome to the forum DrRunCmd.


--- Quote ---f I got Dave right, it only matters for clock lines running in the MHz range.
--- End quote ---
Not quite true. It can make a difference when running signals in parallel. That is why you sometimes see pcb traces in wiggly lines instead of straight lines, to make the trace length the same length.

As magic says, will make little difference in this application.

AVGresponding:
Still, even if it isn't critical, it's good practice, and looks prettier!

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