Principles of Analog Electronics

Principles of Analog Electronics

216

ANSWER

According to Thévenin’s theorem, the

previous bridge topology is equiva-

lent to a voltage source V

TH

in series

with a resistor R

TH

. We have to calculate

them (Figure 6.36).

V

TH

is the voltage “seen” at the output

“1-2” port, so we can determine it as the dif-

ference between the voltage at the node “1”

V

1

, and the one at the node “2” V

2

.

Considering the node connecting V

B

, R

2

,

and R

4

as a reference, we have

V

R

RR

V

B1

2

12

=

+

and

V

R

RR

V

B2

4

34

=

+

therefore

V

R

RR

R

RR

V

TH B

=

+

−

+













2

142

4

34

To determine the value of the resistor R

TH

, we need to nullify the effect of

the voltage source (a short-circuit across it) (Figure 6.37 ...