From: "Steve Andrew"
Subject: Re: Class B amplifiers: what are the large low-value resistors for?
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Date: Thu, 14 Nov 2002 08:02:16 GMT
NNTP-Posting-Date: Thu, 14 Nov 2002 19:02:16 EST
Organization: BigPond Internet Services (http://www.bigpond.net.au)
Ban wrote in message
> "Paul Burridge" schrieb im Newsbeitrag
> > Hi,
> > The circuits I've seen for class b amps mostly seem to have two 0.25
> > - 0.33 ohm resistors between the emitters of the output transistors
> > concerned. Are they really necessary at all? And if I don't have these
> > ultra-low values to hand, can I get away with 1ohm ones and what would
> > be the effect on performance?
> > Thanks.
> > --
> > Noverint universi per presentes et futuri...
> quod anno Domini millesimo quatercentesimo octuagesimo secundo...
> Do you want to demonstrate your ability reading Latin or is it just
> This was written 1500 yrs. before, now give a guess:
> Aurea prima sata est aetas, quae vindice nullo,
> sponte sua, sine lege fidem rectumque colebat.
> poena metusque aberant, nec verba minantia fixo
> aere legebantur, nec supplex turba timebat
> iudicis ora sui, sed erant sine vindice tuti.
> The emitter resistors are needed to stabilize the bias current and/or if
> parallel a couple of output transistors, to achieve a higher current drive
> capability. You can take higher values, but have to recalculate well the
> required power handling capability and you will loose this power on the
> loudspeaker. You might also have to modify the bias current adjustment.
> BTW the values are easily available in any shop.
> ciao Ban
> electronic hardware designer
Non potes composituram machinarum quae apte musicam facuint emere monoris
quam mille. (You can't get a decent sound system for under a grand) ;->