Re: BJT transistor beta, vs Ebers-Moll, Gummel-Poon, and the other tools God has given us

From: John Popelish (jpopelish_at_rica.net)
Date: 12/08/04 

Date: Tue, 07 Dec 2004 20:17:44 -0500

Don Pearce wrote:

> Everything obeys Ohms law. Whatever the condition, V/I=R. OK, so R
> changes - V and I change accordingly. Ohms law is still obeyed.

Ohm's law applies only to things that hold a constant (or reasonably
nearly so) ratio of voltage to current over some range of voltage and
current. Just dividing an arbitrary voltage drop caused by an unknown
process by the current passing through that process does not define
the process resistance if that ratio is not predictive of the voltage
at a different current or vice versa. Processes that have non
constant ratios of voltage drop to current are called non ohmic for a
reason. And that reason is that ohm's law does not apply to them. 

-- 
John Popelish

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