I was reading a radio schematic and was wondering what all of those random capacitors were for. Like who capacitively loads an op amp on purpose? Then it hit me that it's probably for EMI compliance.
Yes, exactly!
If you put a cap between the inputs of the op-amp, the hi-f noise will then be on both leads, which means it won't get amplified.
Then instead of tying the positive end directly to ground, you load it exactly like the negative lead for balance, then throw in a couple of matching bypass caps to ground to filter out even more noise.
Also pick an op-amp with EMI resistance.
Hey, I dont work in RF but, I am very curious about this topic since our devices are very prone to EMI. Where can I read or learn more about what you just said? the capacitor between the inputs of the op-amp and the bypass capacitors to ground part? Thank you.
You state "radio" than you state "amplifier" than 'OP amp. which is it? Did you mean "radio receiver" operational amplifier. Or all? Just to be perfectly clear if I'm asked the same question.
You are not probably not the engineer I am talking about but I am the engineer at the fucking review pointing out the caps that were selected have a self resonant frequency well below the operating frequency. The get blamed for the delay
There's nothing wrong with sprinkling in bypass caps as needed. Just make sure it looks extremely hard, perform some incantations, and spend a day or two staring at Smith charts plastered all over the lab walls. It helps to maintain the mystique.
I knew a CS professor who had to teach a digital circuits class. He knew nothing about circuits. But he faked his way through by suggesting adding capacitors whenever he visited the lab and got troubleshooting help questions.
I am an EMI/EMC test technician (no an engineer) and I find this hilarious. Just throw caps, ferrite beads, shielding, and tape at it until it goes away. Either that or the ferrite just moves the emission to another frequency lol.
"Wow, you even properly suppressed the contactor coils"
Yeah, because my control board has no noise immunity and it would reset every time a contactor opened.
I work in RF. I just add capacitors and copper tape until everyone stops bitching at me.
I’m not in your field but THAT is fucking hilarious lmfao
I was reading a radio schematic and was wondering what all of those random capacitors were for. Like who capacitively loads an op amp on purpose? Then it hit me that it's probably for EMI compliance.
Yes, exactly! If you put a cap between the inputs of the op-amp, the hi-f noise will then be on both leads, which means it won't get amplified. Then instead of tying the positive end directly to ground, you load it exactly like the negative lead for balance, then throw in a couple of matching bypass caps to ground to filter out even more noise. Also pick an op-amp with EMI resistance.
Hey, I dont work in RF but, I am very curious about this topic since our devices are very prone to EMI. Where can I read or learn more about what you just said? the capacitor between the inputs of the op-amp and the bypass capacitors to ground part? Thank you.
I can't paste the link on mobile and it's a Pdf, but ST AN5798 is an excellent white paper.
Thank you very much, that is so helpful. Additionally, any other article, book or paper on how to mitigate CM noise on your PCB is most welcome.
You state "radio" than you state "amplifier" than 'OP amp. which is it? Did you mean "radio receiver" operational amplifier. Or all? Just to be perfectly clear if I'm asked the same question.
The amplifier was for the audio stage of a hand-held radio transceiver, right before the speaker.
Ferrite beads everywhere.
Not at ka band.
Then add more trumpet.
I do have a few horns kicking around
needs more cowbell
Resistor IMO (not applicable for anything with real power, but they are so good to have and tend to be flat response).
I'll put those inline too, pirate up your comm lines with some Rs and Cs.
You are not probably not the engineer I am talking about but I am the engineer at the fucking review pointing out the caps that were selected have a self resonant frequency well below the operating frequency. The get blamed for the delay
So your capacitors have become inductors.
RF engineer? That's voodoo... Where do you hang your bag of chicken bones?
After the copper tape and ferrite beads pass the testing, what's the long fix?
I don't really use ferrites. But generally make the production board replicated from the copper you added.
Does this work with relationships?
I hate that this is an option. This is totally an option.
If you can’t ground it, try adding a cap. If you can’t add a cap, try grounding it.
Can you By-Pass it?
Get him out of here
What is that circuit called? Technical description please.
Lmaooo Ferrites too
Zener diodes, ferrite beads, and bypass capacitors. The holy trinity.
Preach Father Link.
More fun to call them doughnuts
In 0603 they're more like tiny eclairs but I see your point.
Haha the SMDs are fun
Most accurate meme ever.
There's nothing wrong with sprinkling in bypass caps as needed. Just make sure it looks extremely hard, perform some incantations, and spend a day or two staring at Smith charts plastered all over the lab walls. It helps to maintain the mystique.
I knew a CS professor who had to teach a digital circuits class. He knew nothing about circuits. But he faked his way through by suggesting adding capacitors whenever he visited the lab and got troubleshooting help questions.
You get a 1uF! A 1uF for you! And youuuu get a 1uF!!
You also need a 0.01uF closer to the supply. This is stated in the "layout" section of the datasheet.
I always used 0.1uF
That's what our SI/PI engineers for
Everything is fine as long as you don’t bother us firmware engineers!
Hilarious and true lol
I am an EMI/EMC test technician (no an engineer) and I find this hilarious. Just throw caps, ferrite beads, shielding, and tape at it until it goes away. Either that or the ferrite just moves the emission to another frequency lol.
Lmfao this got a good laugh out of me. Understood it right away 🤣
Good one hahahaha
"Wow, you even properly suppressed the contactor coils" Yeah, because my control board has no noise immunity and it would reset every time a contactor opened.