AD704

REV. A

–8–

14-Pin Cerdip (Q) Package

16-Pin Plastic SO (R) Package

14-Pin Plastic DIP (N) Package

20-Terminal LCCC (E) Package

0.358 (9.09)

0.342 (8.69)

NO. 1 PIN

INDEX

0.040 (1.02)

x 45

° REF

3 PLCS

0.020 (0.51)

x 45

° REF

0.050

(1.27)

BSC

0.100 (2.54)

0.064 (1.63)

0.028 (0.71)

0.022 (0.56)

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

Table II. 1 Hz, 4-Pole Low-Pass Filter Recommended Component Values

Section 1

Section 2

Desired Low

Frequency

Frequency

C1

C2

C3

C4

Pass Response

(Hz)

Q

(Hz)

Q

( F)

( F)

( F)

( F)

Bessel

1.43

0.522

1.60

0.806

0.116

0.107

0.160

0.0616

Butterworth

1.00

0.541

1.00

1.31

0.172

0.147

0.416

0.0609

0.1 dB Chebychev

0.648

0.619

0.948

2.18

0.304

0.198

0.733

0.0385

0.2 dB Chebychev

0.603

0.646

0.941

2.44

0.341

0.204

0.823

0.0347

0.5 dB Chebychev

0.540

0.705

0.932

2.94

0.416

0.209

1.00

0.0290

1.0 dB Chebychev

0.492

0.785

0.925

3.56

0.508

0.206

1.23

0.0242

Specified Values are for a –3 dB point of 1.0 Hz. For other frequencies simply scale capacitors C1 through C4 directly; i.e., for 3 Hz Bessel response, C1 = 0.0387

µF,

C2 = 0.0357

µF, C3 = 0.0533 µF, C4 = 0.0205 µF.

The 1 Hz, 4-pole active filter offers dc precision with a mini-

Ω resistors without sacrificing the

1

µV/°C drift of the AD704. This means lower capacitor values

may be used, reducing cost and space. Furthermore, since the

ture range, most applications do not require the use of the

normal balancing resistor (with its stability capacitor). Adding the

optional balancing resistor enhances performance at high

temperatures, as shown in Figure 26. Table II gives capacitor

values for several common low pass responses.

180

120

60

0

–60

–120

–180

–40

0

+40

+80

+120

WITHOUT OPTIONAL

BALANCE RESISTOR, R3

TEMPERATURE – C

o

WITH OPTIONAL

BALANCE RESISTOR, R3

Filter Circuit