IEEE TRANSACTIONS ON EDUCATION, VOL. 41, NO. 2, MAY 1998 171

Correspondence

Comment on “On the Geometry of Parallel Impedances”

Vittal P. Pyati

In the above paper1 the time-honored custom of forbidding the useof angle-measuring devices in geometrical proofs appears to havebeen violated by its author Karni. If it were otherwise, the problem oftrisecting an arbitrary angle would be trivial. Furthermore, the methodproposed by Karni suffers from the disadvantage of employing oneprocedure for resistors and another for impedances. This is boundto prove awkward when there is a combination of the two. By farthe most elegant geometrical method of handling impedances andresistors connected in parallel is that of inversion in a circle followedby reflection in the real axis. This requires that the impedances begiven in rectangular rather than polar form. I learned the inversionmethod (invented in the West at least a 100 years ago) in the 1950’s asan undergraduate in my native India. In the modern age of computers,graphical methods can perhaps play a supplementary role.

For technical reasons, manuscript received April 29, 1997.The author is with the Department of Electrical and Computer Engineering,

Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433USA.

Publisher Item Identifier S 0018-9359(98)03414-1.1S. Karni, IEEE Trans. Educ., vol. 35, pp. 233–234, Aug. 1992.

Correction to “On Optimizing the FeedbackComponents in a Voltage-Feedback Amplifier”

Philip Hoff

In the above paper,1 there is an error in Fig. 4. Only one of theloading factors was incorporated into the PSPICE simulations. Theother one effectively lowers the unbypassed emitter resistance in thefirst stage and so increases the open-loop gain slightly. The revisedFig. 4 is included with this correction. The simulation predicts themaximum open-loop gain forRu = 78 : To the nearest wholenumber, this is the same value predicted by the original Fig. 4, sonone of the conclusions is modified.

Manuscript received August 1997.The author is with the O’Connell Technology Center, California State

University-Chico, Chico, CA 95929-0888 USA.Publisher Item Identifier S 0018-9359(98)03415-3.1P. Hoff, IEEE Trans. Educ., vol. 40, pp. 219–221, Aug. 1997

0018–9359/98$10.00 1998 IEEE