Norton impedance

To determine the Norton equivalent impedance ZG in Figure 2.36, we can kill all the sources in circuit A and then calculate the impedance from n-n terminals by looking back into circuit A. Thus, the Norton impedance ZG is equal to the Thevenin impedance. The Norton current IQ is a constant current that remains the same regardless of the impedance of circuit B. It can be determined by... 

For more complex current sources, it is necessary to employ Norton s theorem0 which states that any linear network of impedances and voltage sources can be substituted by an equivalent circuit containing a current source iN in parallel with an impedance 2 x, where iN is the current which flows when the output terminals of the network are short-circuited and 2EX is the network impedance with all source voltages put equal to zero and replaced by their internal impedances. 

Similar to Thevenin s theorem, Norton s theorem states that a section of a linear circuit containing one or more sources and impedances can be replaced with an equivalent circuit model containing only one constant current source and one parallel-connected impedance, as shown in Figure 2.36. 

Bobadma AD, BeUido EP, Rangel NL, Zhong H, Norton ML, Sinitskii A, Seminario JM (2009) DNA origami impedance measurement at room temperature. J Chem Phys 130 171101... 

Acoustic transmission measurements were made on a Norton-supplied tensile bar in the molded state. Because this material had not been tested acoustically, there was uncertainty as to the value of its properties, particularly attenuation. PAD found that at 5 MHz, attenuation was sufficiently low that a through transmission signal was easily obtained through the length of the sample. This may allow conducting velocity measurements across the samples at frequencies as high as 20 to 50 MHz, yielding measurement accuracy considerably better than 1%. The velocity and impedance obtained for this sample were 2.3 mm/sec and 5.3 MR, respectively. 

---