Wideband Noise

The wideband noise of the filter is the total RMS value

of the device’s noise spectral density and is used to

determine the operating SNR. Most of its frequency

contents lie within the filter’s passband and cannot be

reduced with postfiltering. The total noise depends

mainly on the Q of each filter section and the cascade

sequence. Therefore, in multistage filters, the section

with the highest Q should be placed first for lower out-

put noise.

Multiple Filter Stages

In some designs, such as very narrow band filters, or in

without multiple feedback. The total Q of the resultant

Q is the Q of each individual filter section, and N is the

number of 2nd-order sections. In Table 5, the total Q

and total bandwidth (BW) are listed for up to five identi-

cal 2nd-order sections. B is the bandwidth of each sec-

tion.

Chip Information

TRANSISTOR COUNT: 1439

TECHNOLOGY: BiCMOS

Dual Universal Switched-Capacitor Filters

16

______________________________________________________________________________________

TOTAL SECTIONS

TOTAL BW

TOTAL Q

1

1.000 B

1.00 Q

2

0.644 B

1.55 Q

3

0.510 B

1.96 Q

4

0.435 B

2.30 Q

5

0.386 B

2.60 Q

Table 5. Cascading Identical Bandpass

Filter Sections