From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: type of NPN transistor for minimul voltage drop C to E
References: <6jzD9.165153$MGm1.firstname.lastname@example.org> <email@example.com>
Date: Sat, 23 Nov 2002 08:30:44 GMT
NNTP-Posting-Date: Sat, 23 Nov 2002 00:30:44 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Spehro Pefhany wrote:
> On Fri, 22 Nov 2002 23:44:02 GMT, the renowned "Brill Pappin"
> >Any ideas an what type of transistor I should look at to get the minimum
> >voltage drop when on (NPN)?
> >A typical diode (1N4001 you can expect about .6V (rule of thumb) a
> >transistor will be about the same (give or take) is there a particular type
> >that will have significantly less voltage drop?
> No, a saturated silicon BJT (transistor) will be < 100mV from
> collector to emitter, in most cases, for a small signal transistor.
> Best regards,
> Spehro Pefhany
> "it's the network..." "The Journey is the reward"
> firstname.lastname@example.org Info for manufacturers: http://www.trexon.com
> Embedded software/hardware/analog Info for designers: http://www.speff.co
Not quite correct.
A small signal NPN driven in the standard configuration will give a
nominal Vce from 50mV to 200mV depending on the collector current.
However, if one interchanges the emitter and collector and does not
mind rather low betas (maybe 0.01 to 1), the Vce can be under 10
Remember, the typical "collector" breakdown now will be 6V (the
transistors' Vbe breakdown rating).
This "trick" was well known in the early 1970s.
However, if one dislikes the base-"collector" interaction, then use a