STMicroelectronics 1.2 W fully differential audio power amplifier DEMOTS4995J DEMOTS4995J Data Sheet

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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

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.

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

●

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.

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

CC

/2 for any DC common mode bias input voltage.

Due to the V

IC

 limitation of the input stage (see 

), the common mode 

feedback loop can fulfil its role only within the defined range. 

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.

Ω 

From 

, 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

×

=