13/24

L6258E

so the gain of this block is:

where:

Before analysing the error amplifier block and the sense transconductance block, we have to do this consider-

ation :

and

this means that Ax|dB is the sum of the power amplifier and load blocks;

The BODE analysis of the transfer function of Ax is:

Figure 8.

The Bode plot of the Ax|dB function shows a DC gain of -1.9dB and a pole at 163Hz.

It is clear now that (because of the negative gain of the Ax function), Bx function must have an high DC gain in

ACload

V

sense

v

out

------------------

R

S

R

L

R

S

+

---------------------

==

ACload

dB

20

R

S

R

L

R

S

+

---------------------

log

⋅

=

Aload

dB

20

0.33

12

0.33

+

------------------------

log

⋅

31.4dB

–

==

Fpole

1

2

π

L

L

R

L

R

S

+

---------------------

⋅

---------------------------------

=

Fpole

1

6.28

12 10

3

–

⋅

12

0.33

+

------------------------

⋅

-----------------------------------------

163Hz

==