TS472

Application information

Doc ID 11015 Rev 6

13/25

4

Application information

4.1

Differential configuration principle

The TS472 is a fully-differential input/output microphone preamplifier. The TS472 also

includes a common-mode feedback loop that controls the output bias value to average it at

VCC/2. This allows the device to always have a maximum output voltage swing, and by

consequence, maximize the input dynamic voltage range.

The advantages of a fully-differential amplifier are:

●

Very high PSRR (power supply rejection ratio).

●

High common mode noise rejection.

●

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

better to keep this option.

4.2

Higher cut-off frequency

The higher cut-off frequency FCH of the microphone preamplifier depends on the external

capacitors C1, C2.

TS472 has an internal first order low-pass filter (R = 40 k

Ω, C = 100 pF) to limit the highest

cut-off frequency on 40 kHz (with a 3 dB attenuation). By connecting C1, C2 you can

decrease FCH by applying the following formula.

Figure 32 represents the higher cut-off frequency in Hz versus the value of the output

capacitors C1, C2 in nF.

Figure 32.

Higher cut-off frequency vs. output capacitors

For example, FCH is almost 20 kHz with C1,2 =100 pF.

F

CH

1

2

π 40

3

× 10

C

12

,

100

12

–

× 10

+

()

⋅⋅

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

=

200

400

600

800

1000

1

10

C1, C2 (pF)

40