Hi Ed,
I know through artifice that you can create plots
of a tunnel diode. A 576 will do it directly, but
it does not match the actual operation of the part,
When the TD gets to the threshold current, it instantly
drops to the lower threshold point. It doesn't wander
lackadaisically down as the curve shows.
The curve shows as it does because it is so totally
swamped by the capacitance of the analyzer that it
smears a trace from the last point where the V/I was
to where it has switched to.
-Chuck Harris
Ed Breya via Groups.Io wrote:
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Regarding the tunnel diode branch from this thread - it is indeed possible to see the complete I-V curve of a tunnel diode in low frequency or DC conditions. Normal curve tracers can't do it because their series R is too high, so it appears discontinuous. Specially made, very low resistance test fixtures can suppress the instability caused by the TD's negative R, allowing display of the actual I-V - even that magical negative R region.
You can find such a test circuit in either (or maybe both - I forget) the GE or RCA TD manuals from the 1960s. The circuit displays the I-V on a scope, just like a curve tracer, but it's dedicated to only this function. I had once thought about building one of these, for curiosity, but for general go-no-go testing of TDs, it's not really necessary to see that part anyway. You can trust that the TD is doing its thing if you can see the endpoints, on a regular curve tracer, or in-circuit.
Ed
