STMicroelectronics 1.2 W fully differential audio power amplifier DEMOTS4995J DEMOTS4995J Scheda Tecnica
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DEMOTS4995J
TS4995
Application information
17/26
4 Application
information
4.1 Differential
configuration
principle
The TS4995 is a monolithic full-differential input/ output power amplifier with fixed +6 dB
gain. The TS4995 also includes a common mode feedback loop that controls the output bias
value to average it at V
gain. The TS4995 also includes a common mode feedback loop that controls the output bias
value to average it at V
CC
/2 for any DC common mode input voltage. This allows maximum
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.
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:
●
V
ery high PSRR (power supply rejection ratio)
●
High common mode noise rejection
●
Virtually no pop and click without additional circuitry, giving a faster start-up time
compared to conventional single-ended input amplifiers
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.
However, to reach maximum performance in all tolerance situations, it is recommended to
keep this option.
4.2
Common mode feedback loop limitations
As explained previously, the common mode feedback loop allows the output DC bias voltage
to be averaged at V
to be averaged at V
CC
/2 for any DC common mode bias input voltage.
Due to the V
IC
), the common mode
feedback loop can fulfil its role only within the defined range.
4.3
Low frequency response
The input coupling capacitors block the DC part of the input signal at the amplifier inputs. C
in
and R
in
form a first-order high pass filter with -3 dB cut-off frequency.
Note:
The input impedance for the TS4995 is typically 20k
Ω
and there is tolerance around this
value.
, you can easily establish the C
in
value required for a -3 dB cut-off frequency.
)
Hz
(
C
R
2
1
F
in
in
CL
×
×
π
×
=