Hi all,

may I ask you a question please?

I am building a large circuit on breadboards, with lots of IC's. And I am wondering what is the best way to decouple each IC from the power supply ?

I have added one 100nF capacitor per IC, but the way I attached these capacitors is as follows, each capacitor has one leg as close as possible to Vdd of each IC, however the other leg is far away from the GND of the IC's. That's because I am putting the capacitors directly at the power rails from rail to rail.

Does this work? Also i have thought of adding one extra capacitor per IC, connected the same way as above but close to the GND of each IC rather than Vdd.

Should the capacitors be connected in a different way? Should them be with one leg at Vdd and the other at GND directly? Like above the IC. This makes the legs rather long which is of concern,,,

Please help...

Thank you !

 

One decoupling cap per power lead on each IC is the most conservative design. If you don't have ground or power planes, you can't avoid long leads. I'd do as you're doing.

Most guidelines will also have you add some electrolytic caps for better low frequency decoupling.

 

Please take a clear photo for the breadboards as 800x600 jpg, it may more easy to see your problem.

 

I am building a large circuit on breadboards,

as you are building it on a breadboard, you cannot be working on super-high frequencies or high current levels. I wouldn't worry too much about it.

 

as you are building it on a breadboard, you cannot be working on super-high frequencies or high current levels. I wouldn't worry too much about it.

Thank you. Actually it will be running at around 4MHz, is that ok ?

 

Please take a clear photo for the breadboards as 800x600 jpg, it may more easy to see your problem.

Thank you. I will do.

 

as you are building it on a breadboard, you cannot be working on super-high frequencies or high current levels. I wouldn't worry too much about it.

I've had high frequency noise problems on breadboards that were solved by decoupling even when my signals were audio frequencies.

 

each capacitor has one leg as close as possible to Vdd of each IC, however the other leg is far away from the GND of the IC's. That's because I am putting the capacitors directly at the power rails from rail to rail.

Doesn't the ground rail go close to the ground pins on the IC's?
It should.

 

Doesn't the ground rail go close to the ground pins on the IC's?
It should.

The first time I did it, I connected one leg to Vdd, but the other wat at a ground far away from the IC's ground. But now they are connected from Vdd to GND directly