R =

M

2n

2

(8)

n

n

1:n

Figure 8-9. Driver Peak Output Model

With the required output voltage and current versus turns ratio set, an output stage headroom model allows the

required supply voltage versus turns ratio to be developed.

The headroom model (see Figure 8-10) can be described with the following set of equations:

First, as available output voltage for each amplifier:

V

=V

(V +V )

I

(R +R )

-

OPP

CC

1

2

-

´

P

1

2

(9)

Or, second, as required single-supply voltage:

V

=

CC

1

2

V

+(V +V )+I

(R +R )

OPP

1

2

(10)

V

O

R

1

V

1

+V

CC

R

2

V

2

I

P

Figure 8-10. Line Driver Headroom Model

Table 8-1. Line Driver Headroom Model Values

0.9 V

2 Ω

0.9 V

2 Ω

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SBOSAA5B – APRIL 2022 – REVISED SEPTEMBER 2022

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