Re: bypass cap?

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

206.233.68.152

In Reply to: Re: bypass cap? posted by JZ on January 15, 2000 at 03:37:05:

I think the real confusion is that engineers and techs take for granted the knowledge accumulated over the years when discussing these techniques and forget that the terminolgy is the same for different kinds of bypasses, even though amongst themselves there is agreement based on the context (got that?).
In this instance (op-amp applications) a bypass of the op-amp is the placement of a capacitor between the op-amp power supply pins and the ground plane. This is done to provide a path for AC radio-frequency (RF) garbage that might be contaminating the DC power supply rails. RF hash can cause op-amps to mis-behave in a lot of ugly ways, but generally because they have a large open-loop bandwidth they can oscilate when the gunk gets inside the power rails inside the op-amp via the supply pins.
In power supplies a bypass capacitor of small value is usually is placed in parallel with a large capacitor to provide sonic benefits. The bypass in this case is usually of a film type and doesn't really contribute to the capacitance or energy storage of the power supply, its purpose is to provide a lower series resistance path, and the benefit of a faster response to time-varying voltages( an audio signal). There is a lot more to the subject, and I am hardly an authority, you might check out Richard Marsh's papers available at reliablecapacitors.com, for in-depth review of the variety of way capacitor bypasses are implemented, and other intelligent stuff. Did this help?

This post is made possible by the generous support of people like you and our sponsors:

Schiit Audio

Follow Ups Full Thread

Topic - ad712, ne5334 opampsreplacements, need help! - JZ 14:21:25 01/13/00 (8)

Re: ad712, ne5334 opampsreplacements, need help! - bobwire 12:58:22 01/14/00 (3)

Re: bypass cap? - JZ 03:37:05 01/15/00 (2)

Re: bypass cap? - patentguy 14:22:49 01/15/00 (1)

Re: sorry my mistake,besides if you haven't heard of this try it! - JZ 17:34:42 01/15/00 (0)

ad712 replacements - Ed Hsu 17:28:38 01/13/00 (3)

Re: ad712 replacements - JZ 00:56:54 01/14/00 (2)

Re: ad712 replacements - Ed Hsu 07:20:33 01/14/00 (1)

Re: ad712 replacements - JZ 17:38:36 01/15/00 (0)

Follow Ups

Re: bypass cap? - patentguy 14:22:49 01/15/00 (1)

Re: sorry my mistake,besides if you haven't heard of this try it! - JZ 17:34:42 01/15/00 (0)

You can not post to an archived thread.