TS488 datasheet(24/32 Pages) STMICROELECTRONICS

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Application information

TS488-TS489

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Note:

In case FCL is kept the same for calculation, It must be taken in account that the

1st order high-pass filter on the input and the 1st order high-pass filter on the

output create a 2nd order high-pass filter in the audio signal path with an

attenuation 6dB on FCL and a roll-off 40db⁄ decade.

4.4

Higher cut-off frequency

In the high frequency region, you can limit the bandwidth by adding a capacitor Cfeed in

parallel with Rfeed. It forms a low-pass filter with a -3dB cut-off frequency FCH. Assuming

that FCH is highest frequency to be amplified (with a 3dB attenuation), the maximum value of

Cfeed is:

Figure 79.

Lower cut-off frequency vs.

input capacitor

Figure 80.

Lower cut-off frequency vs.

output capacitor

100

1000

100

10k

Rin=50k

Rin=100k

Rin=20k

Cin (nF)

Rin=10k

0.1

100

1000

100

10k

=32

=600

=16

Cout (

μF)

Figure 81.

Higher cut-off frequency vs. feedback capacitor

π R

feed

⋅⋅

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

0.01

0.1

100

10k

100k

Rfeed=40k

Rfeed=80k

Rfeed=20k

Cfeed

(

μF)

Rfeed=10k

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