The Maplin Electronic Circuits Handbook, 2nd Edition

28 PASSIVE COMPONENTS

Input

Output

Figure 1.14 T-network

attenuator (unbalanced)

ri Hi

Input R*

Output

X

Figure 1.15 π-network

attenuator (unbalanced)

Input R

2

«1

I

Output

Figure 1.16 H-network

attenuator (balanced)

The design formulae for these circuits are as follows:

Table 1.3

Attenuator type

Resistor

Τ

π

Η

(x-\)

Ζ

(x

2

-l)

Ζ

2x

Z(x-\)

2(x+\)

R

2

z

z

(x+\) 2x

R

2

(χ

2

-ί)

(x-i)

(x

2

-l)

Where Ζ is the design impedance of the network (often 600 Ω for line

matching purposes) and χ is the desired ratio of input to output voltage

(i.e.x=K

in

/K

out

).

Where attenuation is to be expressed in decibels (dB) the table given in

Chapter 4 may be used.

For radi ...