Application information

TS4998

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Application information

4.1

General description

The TS4998 integrates two monolithic full-differential input/output power amplifiers with two

selectable standby pins dedicated for each channel. The gain of each channel is set by

external input resistors.

4.2

Differential configuration principle

The TS4998 also includes a common mode feedback loop that controls the output bias

output voltage swing, and therefore, to maximize the output power. Moreover, as the load is

connected differentially instead of single-ended, output power is four times higher for the

same power supply voltage.

The advantages of a full-differential amplifier are:

●

High PSRR (power supply rejection ratio),

●

High common mode noise rejection,

●

Virtually no pops&clicks without additional circuitry, giving a faster startup time

compared to conventional single-ended input amplifiers,

●

Easier interfacing with differential output audio DAC,

●

No input coupling capacitors required due to common mode feedback loop.

In theory, the filtering of the internal bias by an external bypass capacitor is not necessary.

However, to reach maximum performance in all tolerance situations, it is recommended to

keep this option.

The only constraint is that the differential function is directly linked to external resistor

mismatching, therefore you must pay particular attention to this mismatching in order to

obtain the best performance from the amplifier.

4.3

Gain in typical application schematic

A typical differential application is shown in Figure 1 on page 3.

The value of the differential gain of each amplifier is dependent on the values of external

is expressed by the relation given in Equation 1.

Equation 1

feedback resistors).

A

V

diff

V

O+

V

O-

–

Diff

input+

Diff

input-

–

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

R

feed

R

IN

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

50k

Ω

R

IN

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

==

=