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Article #15423Re: Query - How valves and transistors work
From: Duncan Barclay
Date: Sun, 03 Jan 1999 00:00
Date: Sun, 03 Jan 1999 00:00
32 lines
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3119 bytes
In article <ORcwZBAvyxj2Ewox@jmwa.demon.co.uk>, John Woodgate <jmw@jmwa.demon.co.uk> writes: > <76lqli$ra5$1@computer.my.domain>, Duncan Barclay > <dmlb@ragnet.demon.co.uk> wrote: > > John Woodgate wrote: >>If one adopts this concept >>> exclusively, it appears that it is not possible to make a linear (non- >>> grossly distorting) amplifier. >> >>Use feedback, or apply the small signal approach. The classic four >>resistor CE amplifier is linearised by the negative feedback generated >>by the emitter resistance. Emitter followers are the same, so are common >>base. > > No, when we used discrete transistors as amplifiers, we decoupled the > emitter resistor. And the AC swing in vbe is still very small. You have linearised the BJT by biasing it at a quiscent DC collector current. Small signal vs. large signal. The decoupling of the emitter resistor ensures that the transconductance for ac signals is gm=IC/VT=gm0 instead of gm=gm0/(1+gm0*RE). Duncan -- ________________________________________________________________________ Duncan Barclay | God smiles upon the little children, dmlb@ragnet.demon.co.uk | the alcoholics, and the permanently stoned. ________________________________________________________________________
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fcc1a,6f59d673fceaf3aa X-Google-Attributes: gidfcc1a,public X-Google-Thread: 114713,6f59d673fceaf3aa X-Google-Attributes: gid114713,public X-Google-Thread: 112d1e,6f59d673fceaf3aa X-Google-Attributes: gid112d1e,public X-Google-Thread: 111d0a,6f59d673fceaf3aa X-Google-Attributes: gid111d0a,public X-Google-Thread: 107d45,6f59d673fceaf3aa X-Google-Attributes: gid107d45,public X-Google-Thread: 1110fe,6f59d673fceaf3aa X-Google-Attributes: gid1110fe,public X-Google-Thread: 10b271,6f59d673fceaf3aa X-Google-Attributes: gid10b271,public X-Google-Thread: 1118be,6f59d673fceaf3aa X-Google-Attributes: gid1118be,public From: dmlb@ragnet.demon.co.uk (Duncan Barclay) Subject: Re: Query - How valves and transistors work Date: 1999/01/03 Message-ID: <76nqh9$nf$2@computer.my.domain> X-Deja-AN: 428332089 Distribution: world X-NNTP-Posting-Host: ragnet.demon.co.uk:158.152.46.40 References: <368691bc.0@stargazer.actinet.net> <76b08g$jo4$1@news-1.news.gte.net> <76b8i0$rqm$1@computer.my.domain> <fuNEGVAumei2EwR5@jmwa.demon.co.uk> <76dss3$fhq$1@computer.my.domain> <d1dLzCAjKri2EwAr@jmwa.demon.co.uk> <76ibj9$rhc$1@computer.my.domain> <76ja03$gud$1@news-2.news.gte.net> <76jqau$ltt$1@computer.my.domain> <59q9yQA3Bdj2EwN3@jmwa.demon.co.uk> <76lqli$ra5$1@computer.my.domain> <ORcwZBAvyxj2Ewox@jmwa.demon.co.uk> Content-Type: text/plain; charset=us-ascii X-Complaints-To: abuse@demon.net X-Trace: news.demon.co.uk 915381661 nnrp-03:29113 NO-IDENT ragnet.demon.co.uk:158.152.46.40 Organization: Ragnet, a small network of machines at Raggy's home. Mime-Version: 1.0 Newsgroups: sci.physics,fj.sci.physics,sci.physics.electromag,tnn.physics,news.electronics.basics,sci.electronics.basics,sci.electronics.components,sci.electronics.design,sci.electronics.misc