Application Information

TS4994

19/31

4 Application Information

4.1 Differential configuration principle

The TS4994 is a monolithic full-differential input/ output power amplifier. The TS4994 also includes a

common mode feedback loop that controls the output bias value to average it at Vcc/2 for any DC

common mode input voltage. This allows the device to always have a maximum output voltage swing,

and by consequence, maximize the output power. Moreover, as the load is connected differentially

compared to a single-ended topology, the output is four times higher for the same power supply voltage.

The advantages of a full-differential amplifier are:

single-ended input amplifiers.

reach maximal performances in all tolerance situations, it’s better to keep this option.

The main disadvantage is:

maximal performances of the amplifier paying particular attention to this mismatching is mandatory.

4.2 Gain in typical application schematic

Typical differential applications are shown on the figures on page 2.

relation:

Note:

4.3 Common mode feedback loop limitations

As explained previously, the common mode feedback loop allows the output DC bias voltage to be

averaged at Vcc/2 for any DC common mode bias input voltage.

However, due to VICM limitation of the input stage (see Electrical Characteristics on page 4), the

common mode feedback loop can ensure its role only within a defined range. This range depends upon

formula:

with

in

feed

Input

Input

O

O

diff

R

R

.

Diff

.

Diff

V

V

Av

=

−

+

−

=

−

−

+

)

V

(

)

R

R

(

2

R

V

2

R

Vcc

V

feed

in

feed

IC

in

ICM

+

×

×

×

+

×

=

)

V

(

2

.

Diff

.

Diff

V

Input

Input

IC

−

=