Introduction to Electric Circuits

9.5 The inverse hybrid or g-parameters 211

transistors where an additional subscript 'e', 'b' or 'c' is used, depending upon
the configuration (common emitter, common base or common collector,
respectively). Thus we might have for the input impedance hi~ or hlb or hie.
The Equations (9.15) and (9.16) are satisfied by the equivalent circuit shown
in Fig. 9.5.

Figure 9.5

|1

+ o---- ~ h11F ~

U

h12V2

-o

~' h21ll h22

O+

L

V2

O--

9.5 THE INVERSE HYBRID OR g-PARAMETERS

Set 4: If V1 and I2 are the independent variables then the dependent variables

are given by:

I1 = gllV1 = g1212

V2 = g21 V1 + g2212

In matrix form

(9.22)

(9.23)

[,, ]: 121 iv1 }

V2 Lg21 g22 A 12

The parameters of this set are called the inverse hybrid or g-parameters and are
defined as follows:
9 g~a is the input admittance (gi) and is measured in siemens as I~/V1 with
12 = O:
gll = (I1/V1)[&=o (9.25)
9 g21 is the forward voltage gain (gf) and is a dimensionless ratio of voltages
(Vz/V~) with 12 = 0:
g21 = (Vz/V~)I,~=o (9.26)
" g12 is the reverse current gain (gr) and is a dimensionless ratio of currents
(I~/I2) with V~ - 0:
g12- (I~/I2)lv,=o (9.27)