Tunnel diode capacitance test


Miguel Work
 

I have a bunch of russian tunnel diodes, I want to test his capacitance. Any suggestion?
I have a working 7S12 reflectometer, a 7s14, a 500Mhz TDS 5054 scope, a nanovna V2 +, a waynekerr 6425 bridge too. Bridge "only" arrives to 300khz


Regards!


Ed Breya
 

I'd suggest that you don't worry about it. There will be some fixed holder capacitance due to the package, but the rest is non-linear, and depends on bias voltage and circuit conditions. If there are any specs, they would have to be at certain conditions, that you could probably replicate. To make decent measurements, you have to keep the AC signal test voltage as low as possible (like a few to tens of mV) to avoid junction activation and effects. A VNA probably has enough dynamic range to easily handle it with small test signals. The bridge may work too, if it can operate well at low enough voltage.

Ed


Albert Otten
 

I think Michael merely wants to know the capacitances for comparison with specs of the original diodes. In our circuits these diodes are used for switching. It seems that the capacitance during switching is more or less constant and is shown in the specs.
I would measure switching characteristics (rise time and more) and then calculate (in crude ore more refined approximation) the capacitance. For instance the RCA 1963 manual (link at Tekwiki "Tunnel diodes") approximate relations when the load can be neglected.

Albert

On Wed, Sep 15, 2021 at 05:47 AM, Ed Breya wrote:


I'd suggest that you don't worry about it. There will be some fixed holder
capacitance due to the package, but the rest is non-linear, and depends on
bias voltage and circuit conditions. If there are any specs, they would have
to be at certain conditions, that you could probably replicate. To make decent
measurements, you have to keep the AC signal test voltage as low as possible
(like a few to tens of mV) to avoid junction activation and effects. A VNA
probably has enough dynamic range to easily handle it with small test signals.
The bridge may work too, if it can operate well at low enough voltage.

Ed


Albert Otten
 

Sorry Miguel for wrong spelling of your name in my previous message. Albert


Miguel Work
 

:) don´t worry Albert, I have made a little tunnel pulser box to test rise time. I will compare 10mA tunnel diode, AI301G and AI201A. At the moment the first one (<50pF) yields 1,1nS in a 350pS sistem. I will upload some photos. I have replaced the output tunnel diode in a 7T11 with the AI201A, i don´t have more original tektronix diodes.


Miguel Work
 

I have upload some test procedure in photos section

https://groups.io/g/TekScopes/album?id=260881&p=Name,,,20,1,0,0

Diode is valley point biased, I have uploaded calculator in files section too. Direct capacitance reading in NANOVNA is not correct when shunt resistance isn´t infinite or low, I don´t know why. This calculator serves for capacitance calculator with 50 ohms resistor.

AI301G with specs 50 pF has 10pf aprox, and AI201A 5pF, now I have to test rise time with a pulser circuit.

Yesterday I tested self oscillation frequency, and one is about 500Mhz and the other one 1Ghz, thing that agrees capacitance results