TS4994EIKJT STMICROELECTRONICS [STMicroelectronics], TS4994EIKJT Datasheet - Page 23

• Manufacturer Part Number: TS4994EIKJT
• Description: 1.2 W differential input/output audio power amplifier with selectable standby
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

TS4994FC
4
4.1
4.2
Note:
4.3
Application information
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
V
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:
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●
●
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The main disadvantage is:
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Gain in typical application schematic
A typical differential application is shown in
In the flat region of the frequency-response curve (no C
expressed by the relation:
where R
For the rest of this section, Av
Common mode feedback loop limitations
As explained previously, the common mode feedback loop allows the output DC bias voltage
to be averaged at V
However, due to V
mode feedback loop can play its role only within a defined range. This range depends upon
CC
/2 for any DC common mode input voltage. This allows the device to always have a
Very high PSRR (power supply rejection ratio).
High common mode noise rejection.
Virtually zero pop without additional circuitry, giving a faster start-up time compared
with 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. But, to reach maximum performance in all tolerance situations, it is better to
keep this option.
As the differential function is directly linked to the mismatch between external resistors,
paying particular attention to this mismatch is mandatory in order to get the best
performance from the amplifier.
in
= R
in1
= R
ICM
CC
in2
limitation of the input stage (see
/2 for any DC common mode bias input voltage.
and R
A
feed
diff
V
diff
will be called A
=
= R
----------------------------------------------------- -
Diff
feed1
input+
V
O+
= R
Figure 1 on page
–
–
feed2
Diff
V
V
O
to simplify the expression.
input-
.
Table 3 on page
in
=
effect), the differential gain is
R
------------- -
R
feed
in
3.
Application information
5), the common
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