Page 124 - The Art and Science of Analog Circuit Design

James M. Bryant

Figure 9-6.

-V

Although the leads of Cl are short the HF decoupling path of IC1 is far too long.
TTie decoupling path of IC2 is ideal.

correct way to decouple an 1C (IC2 is decoupled by C2 with a very short
decoupling path).

inductors

Any length of conductor has inductance and it can matter. In free space a
1cm length of conductor has inductance of7-10nH (depending on diam-
eter), which represents an impedance of 4-6Q, at 100MHz. This may be
large enough to be troublesome, but badly routed conductors can cause
worse problems as they form, in effect, single turn coils with quite sub-
stantial inductance.

INDUCTANCE Figure $-7,

Any conductor has some inductance
A straight wire of length L and radius R (both mm & L»R)

2L
has inductance 0.2L In -.75 nH

A strip of conductor of length L, width W and thickness H (mm)
has inductance

0.2L

1 cm of thin wire or PC trade is somewhere between 7 and 10 nH

107