Negative Impedance Converter

[quelle]

Hey Guys,
can someone explain me how to calculate the internal Resistance (i know the answer -5kΩ) and the open circuit voltage?

 

[LvW]

What is your definition for "internal resistance"? And at which point do you define the "open circuit" voltage?
Well - let`s assume the "internal" resistance is the input resistance - measured at the non-inv. input terminal of the opamp.
Assuming an ideal opamp (Aol infinite, input resistance infinite), the resulting input resistance Rin at the non-inv. input node is also infinite (because there is no load at the ouput node (Ausgang).
Here is the calculation (without the voltage divider R1-R2) :

Ip=(Vin-Vout)/R3 with Vout=Vn and Vn=Vp=Vin.
Hence, Ip=0 and Rin infinite.

That means, the input resistance into the opamp is infinite and the TOTAL input resistance is R1||R2=+5kOhms.
Without any load impedance at the NIC output we have no negative impedance at all.
Note that the (ideal) NIC conversion function is Rin=(-R3/R4)Rload. (Rin infinite for Rload infinite)

 

[Tha fios agaibh]

Why is the input (Eingang) labeled Vcc?
I think of Vcc as being the + power source. Also, quelle talked about negative impedance or -5 ohms.
Shouldn't that be conductance that's measured in mhos?