I've always seen it as V=IR.
I've always thought about it as R=V/I (resistance is defined by the ratio)
But I've been thinking, is it more accurate to say R= (change in V) / (change in I) ?
It doesnt make a difference if the V vs I curve is linear and goes the V=0 and I = 0
Any other kind of curve (tube transfer function, transistor curves, diode curves, etc.) and you get different results.
I've always thought about it as R=V/I (resistance is defined by the ratio)
But I've been thinking, is it more accurate to say R= (change in V) / (change in I) ?
It doesnt make a difference if the V vs I curve is linear and goes the V=0 and I = 0
Any other kind of curve (tube transfer function, transistor curves, diode curves, etc.) and you get different results.
Is it more accurate to say R= (change in V) / (change in I) ? Any other kind of curve
(tube transfer function, transistor curves, diode curves, etc.) and you get different results.
Yes, for a nonlinear device this is the incremental (or differential) impedance, the slope of the tangent
to the V vs I curve at the operating point, or z = dv/di. This is in general different from the static resistance,
except for perfect resistors. https://en.wikipedia.org/wiki/Electrical_resistance_and_conductance
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Hi,
Yes, for a diode you can only talk about the dynamic impedance,
as its not a resistor it does not follow ohms law, in any sense.
Generally you'd be talking about a devices transconductance variation
rather than the somewhat misleading dynamic resistance concept.
rgds, sreten.
Yes, for a diode you can only talk about the dynamic impedance,
as its not a resistor it does not follow ohms law, in any sense.
Generally you'd be talking about a devices transconductance variation
rather than the somewhat misleading dynamic resistance concept.
rgds, sreten.
Only when the slope or AC or dynamic resistance is the relevant parameter. In other cases V/I is correct. It all depends on context.rif said:But I've been thinking, is it more accurate to say R= (change in V) / (change in I) ?
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