LM4562 decoupling...

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Cant find any definitive information on this and there is no mention of it in the datasheet.

I currently use 47nF polyester film caps. Thinking of trying some R/C decoupling soon. Maybe even experiment with LC.

People must have experimented with this. What were your conclusions as to which cap type and size sounded best (to your ears)?

Also funny how in the datasheet all the graphs stop @ 20khz. Whats going on there....

Any thoughts on this?
 
Tantalums will fail, garantied after some years. Rather thake a modern low ESR like the Pannasonic FM/FC, Robicon ZL/ZLH etc. They are 105° and last a long time.
there are some extremely good Tantal like wet types but then we talk about more then 100,- $ a piece.
No i did no sound comparison but i never whent back.
When i try to make something really good i take 2 x 330uF Nichikon KZ Muse (neutral sound) or 2 x 330uF Elna Silmik 2 ( slightly warmer)and one Röderstein / Vishay MKP1837 0.1uF. Inn case of severe oscilation ( never had one with this arangement and i use very fast OPamps like the AD797 ot LME49713) lokally shunted NPO/COG 4.7nF could help but you have them to solder direct to the pins or a circumferential groundplane.
 
Low ESR caps on power lines can make more damage than good... The rails inductance coupled with the capacitor needs some damping - usually the "normal" ESR is enough for that. If you go with too lower ESR you will get ringing and other artifacts on the rails.
As for the ideea that caps between rails and ground will "dump" noise there - that is nonsense perpetuated by urban legends.
By the way an OpApm is build, the currents will flow thru the ground back to the PS - on each alternance to the other rail. And that's the current you need to bypass!
Not between the rails, that will ADD more current to bypass at the PS on the opposite rail! Bigger loops instead of short ones.
 
Low ESR caps on power lines can make more damage than good... The rails inductance coupled with the capacitor needs some damping - usually the "normal" ESR is enough for that. If you go with too lower ESR you will get ringing and other artifacts on the rails.
As for the ideea that caps between rails and ground will "dump" noise there - that is nonsense perpetuated by urban legends.
By the way an OpApm is build, the currents will flow thru the ground back to the PS - on each alternance to the other rail. And that's the current you need to bypass!
Not between the rails, that will ADD more current to bypass at the PS on the opposite rail! Bigger loops instead of short ones.

Best post so far.....
 
Low ESR caps on power lines can make more damage than good... The rails inductance coupled with the capacitor needs some damping - usually the "normal" ESR is enough for that. If you go with too lower ESR you will get ringing and other artifacts on the rails.

Urban legendary nonsense. Ringing only occurs when there's something to set it off- do bells ring in the absence of being struck? But its true that low ESR caps can do more harm than good... see below.

As for the ideea that caps between rails and ground will "dump" noise there - that is nonsense perpetuated by urban legends.

You're quite welcome to your own opinion. However I've simmed this in LTSpice so the effect is a real one. Ignore it at your peril:D

By the way an OpApm is build, the currents will flow thru the ground back to the PS - on each alternance to the other rail. And that's the current you need to bypass!

As I've set out on another thread where this came up, there are cases where the current from the opamp does not return to ground. When feeding another opamp for example, or when the opamp is feeding into a chipamp.

Not between the rails, that will ADD more current to bypass at the PS on the opposite rail! Bigger loops instead of short ones.

Do please explain this further as I'm not clear where you're coming from.
 
Another interesting post. Thanks :)

As I understand it decoupling is basically the process of isolating one stage of an amplifier or circuit from another. This is traditionally done by a locally placed cap from rail to ground. Its supposed to stop noise entering the next stage right?

How does a cap from +VE to -VE have the same effect in bi-polar situations?

Also, if your LTspice sims prove that the traditional method dumps noise on the GND (which its supposed to do no?), then where does the noise go if the cap is between +/- rails?
 
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