Principles of Analog Electronics

Ampliers: Basic BJT Congurations

411

So, it has been conveniently separated into two terms

Avv

/

vBJT

cb

=

and

vv/.

vi

bs

,

α=

The term A

vBJT

can be considered the voltage gain owing to the BJT

itself, because of the ratio of its output and input voltages. The term

α

vi

,

will

reduce the overall voltage gain A

v

because it takes into account the voltage divider

effect owing to the input loop, as we will see, so this term furnishes an attenua-

tion effect.

A

vBJT

AA

v

v

vBJT

vBJT

c

b

def

The base and collector voltages can be written as

vv vv Ri vR

ii

bbeebe Ee be Eb c

=+=+ =+ +

()

11

vv vv Ri vR

ii

cceece Ee ce Eb c

=+=+ =+ +

()

11

and from Equation II C.E.

v

h

ihi

ce

oe

cf

eb

=−

() ...