Decoupling should be done EVERY time on EVERY chip - analogue or digital - right adjacent to the supply pins.
It costs pretty much nothing, and saves a whole bunch of trouble. Just do it. Part of the need to do this is that chips today are much much faster than they used to be, so where frequency response would roll off before oscillation, nowadays even standard opamps can have GBWs in the MHz to 10s of MHz range, and logic goes far far higher. On the analogue side, I'm currently restoring some Quad amps - the amount of pure twaddle on the www about using loony opamps like the OPA627 and much faster (in "audiophoolery" faster = better) class A drivers & output stages - recipe for high-frequency instability - the circuit were designed to use the inherent limits of the original devices. Maybe I'll just spend 1000 bucks on some speaker cables and unidirectional 99.99999% OFC internal cabling. Not. Nick On Jul 21, 9:50 am, jb-electronics <[email protected]> wrote: > Hi, > > > (2) Sprinkle capacitors across power and ground all over your circuit. > > Preferably as close to the power and ground pins of each chip as > > possible. Usually they're 0.1uf (100nf) ceramic capacitors. Some big > > chips require you to use several near them, so read you datasheets. > > Chips are fast. Very fast. They can either generate very brief short > > circuits (in the ballpark of 10nS), and/or be susceptible to these > > very short glitches on the power rails. > > I cannot stress enough how much pain this will spare you. I recently > built a combined volt- and amperemeter with a 2x16 LCD readout on a > rather small pcb, and I did point-to-point-wiring like I always do, and > it did not want to work. Some weird oscillations at the volts ADC. The > first thing I did was inserting a 100nF cap next to every (!) IC, and > bam, problem solved. > > Jens -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
