Page 230 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

+v

0.1 uf

R1

Vout

le

+Vbias

R M
1_- ---- Q1
2
(e.g ".2N3904)

~
VE

Cin

Vin RE CE

FI GURE 14-5 A common emitter amplifier.
Note that (evsig!(KT/q)) is a modulating factor of the DC quiescent collector current
and represents the AC signal or time-varying signal in the collector current.

So what about the "mysterious" term (evsigICKT/q))? What is that equal to? in Chapter
13 with the introduction to e, it was stated that e = 2.71828 ... = e. And one way
to calculate e is

e = 1 + }I / l + {12/[(2) 1 ]} + {13/ f( (2)(1)]} + ... + [I n/(n! ] = 2.71 2 ...
l
And

x = 1 + xi i I + {x2/( 2 1 n + {xl/re 2) I l} + " " " + [Xlt/ n. 1 14-
where n! is not yelling out n with great loudness (a high school joke), but n! is n

factorial: