🚀 go-pugleaf

Duncan Barclay wrote:
> 
> In article <76b08g$jo4$1@news-1.news.gte.net>,
>         Doug <do@not.spam> writes:
> > Nightjar wrote:
> >>
> >> Could anybody out there tell me how valves and transistors work, please? I
> >> would be eternally grateful.
> >
> > In a couple of sentences or less?
> >
> > Valves are voltage devices.  You can control a relatively
> > large voltage with a small amount of voltage.
> >
> > Transistors are current devices.  You can control a relatively
> > large current with a small amount of current.
> >
> 
> Sorry, you are wrong twice. Both valves and transistors (BJTs and FETs)
> are voltage controlled current sources.
> 
> Valves look like vcvs because they usually are used with small currents
> and large impedances.
> 
> Transistors can look like cccs because they are often used to switch currents
> in low impedance circuits. The base current is essentially a parasitic,
> but fundimental to BJT operation. It is possible to get very high beta
> BJTs by bandgap engineering (hetero-junctions at the base-emitter
> interfaces).
> 
> Duncan
> Duncan Barclay          | God smiles upon the little children,
> dmlb@ragnet.demon.co.uk | the alcoholics, and the permanently stoned.
------------------------------------------------------
In a BJT, collector current is not a function of base voltage, but of
base current, not quite correct, i.e., you cannot double voltage and
double collector current. In a FET you CAN!
-Steve
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