2020 Solution 04

2020 Mar 19, Isaac Abraham
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{2020,3,20,19,42,7.478966}
Consider the Negative Impedance Converter (NIC). Here are some respectable references,​
​(A) NMIMT: Input signal goes into the negative pin of the opamp.​
​(B) TAMU: Input signal goes into the positive pin of the opamp.
Which of the above is the correct circuit for a NIC?
(a) A is correct.​
​(b) B is correct.​
​(c) A and B are correct.​
​(d) Neither A nor B are correct.​
​(e) A is correct only for Z to ground and B is correct only for Z across the gain element.
Your answer
The reason that both are correct follows from the basic mechanism involved in defining impedance (or resistance).
​
Impedance = Voltage/Current.
​
Therefore a negative impedance can be obtained by either
(a) Impedance = (-Voltage)/Current as in Circuit A or
(b) Impedance= (Voltage)/(-Current) as in Circuit B
​