How to connect negative resistance ?

[Michael George]

I was reading this article about negative resistance:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/1868

Would you tell me where the two terminals of negative resistance are, Please ?

Any resistor have two terminals. If I made a negative resistance as shown in the figure, Where are the two terminals?  I need to connect negative resistance in series (or in parallel) with other positive resistors but I don't know how, because I don't know were the terminals of the negative resistor are.

there are three possibilities in my mind:
1- Two terminals are Vin and Vo.
2- Vin and ground.
3- Vo and ground.




Thank you very much,

[Paul Rose]

between Vin and ground

see https://en.wikipedia.org/wiki/Negative_impedance_converter

[Michael George]

@Paul Rose
Thank you for answering my question, I would be very grateful if you would tell me more about this circuit.

Upon your answer "Vin is one of the negative resistor terminals". I will connect Vin to a terminal of a positive resistor. so that they are in series. I expect that the circuit will work like a short circuit, Am I right? If no, How can I connect a positive resistor with the negative resistor?

[Dave]

It wouldn't act like a short, more like a comparator.
If you applied a positive voltage to the input (like in your example), the opamp's output would slam into the positive rail.
If you applied a negative voltage, it would slam into the negative rail.

You can't have it behave like a short, because that would mean that it should be able to pull an infinite current, which would only be possible if there was an infinite voltage across resistor R3.

[Michael George]

So, How can I connect a series positive resistor to a negative resistance op-amp?

[Dave]

The same way you just did.