mark@mips.COM (Mark G. Johnson) (08/08/88)
A candidate for page protector immortality: $ Message-ID: <1308@neoucom.UUCP> Date: 7 Aug 88 18:02:16 GMT $ From: wtm@neoucom.UUCP (Bill Mayhew) $ Subject: Capacitors and solving problems thereof $ ... One of the more important applications (outside tone control $ circuits) for capacitors in audio amplifiers is in $ miller-effect feedback bypass circuits. Miller effect $ feedback involves placing a resistor in the emitter lead of $ a transistor to establish a certain DC operating characteristic $ effectively placing the transistor in a linear amplifying $ modality. The capacitor is placed in parallel with the resistor $ to supply correct AC coupling of the transistor. The problem $ is that the required AC and DC characteristics are often $ different, and thus the capacitor really is necessary. $ It possible to build a so-called direct coupled circuit that $ does not use any capacitors at all, but such a device tends $ to suffer markedly from temperature instibility, gain drift, etc. In addition to being hopelessly befuddled about the Miller effect, the article seems to insist that each amplifier *must* contain a certain capacitor (it "really is necessary"), and that the entire body of experience with DC-coupled amplifiers (including, of course, audio power amplifiers and preamp line-stages) indicates that the DC-coupled topology "suffers markedly" when compared to capacitor-coupled amplifiers. -- -- Mark Johnson MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086 ...!decwrl!mips!mark (408) 991-0208