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Measuring Set Up for Determining the Parasitic Inductance of Capacitors

IP.com Disclosure Number: IPCOM000109579D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Koehler, T: AUTHOR [+3]

Abstract

Capacitor C is connected to a voltage source via a line L with a predetermined characteristic impedance Z. The internal resistance of the voltage source corresponds to the characteristic impedance Z of line L. Because of the low inductance, voltage V2(t) on capacitor C is very small compared with the input voltage V1(t) of line L, so that the latter is considered to be short-circuited and the current curve in the capacitor only depends on the input voltage and the characteristic impedance. It is shown that the integral over the difference in the voltage curve of an ideal capacitor and that of a capacitor which is subject to inductance depends only on the change of the input voltage and the inductance Lc of the capacitor and thus allow that inductance to be readily determined.

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Measuring Set Up for Determining the Parasitic Inductance of Capacitors

       Capacitor C is connected to a voltage source via a line L
with a predetermined characteristic impedance Z.  The internal
resistance of the voltage source corresponds to the characteristic
impedance Z of line L.  Because of the low inductance, voltage V2(t)
on capacitor C is very small compared with the input voltage V1(t) of
line L, so that the latter is considered to be short-circuited and
the current curve in the capacitor only depends on the input voltage
and the characteristic impedance.  It is shown that the integral over
the difference in the voltage curve of an ideal capacitor and that of
a capacitor which is subject to inductance depends only on the change
of the input voltage and the inductance Lc of the capacitor and thus
allow that inductance to be readily determined.  As the wiring and
its characteristic impedance are considered by the relevant
calculations, the result remains unaffected.

                            (Image Omitted)

Probe 1   measures voltage ramp at input of line L.
Probe 2   measures voltage response at capacitor C, assuming that
V2(t)<< V1(t).  Therefore, line L is considered to be short-
circuited at the end for calculating ic(t):
                     V1(t - TD)
           ic(t) = 2 __________
                          Z
           ?V2dt is derived from the cur...