LS404I データシートの表示（PDF） - STMicroelectronics

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LS404I

HIGH PERFORMANCE QUAD OPERATIONAL AMPLIFIER

STMicroelectronics 

Fixed R = R1 = R2, we have (see figure 13)

C1 = R-1-- -ω--ζ--c-

Figure 13 : Filter Configuration

C 2 = R-1-- ξ----ω1-----c-

R1

Vin

C2

R2

C1

LS404

Vout

Three parameters are needed to characterize the

frequency and phase response of a 2nd order ac-

tive filter: the gain (Gv), the damping factio (ξ) or

the Q factor (Q = 2 ξ)1), and the cuttoff frequency

(fc).

Table 1

Filter Response

ξ

The higher order response are obtained with a se-

ries of 2nd order sections. A simple RC section is

introduced when an odd filter is required.

The choice of ’ξ' (or Q factor) determines the filter

response (see table 1).

Q

Cuttoff Frequency fc

Bessel

-----3-

-----1-

Frequency at which Phase Shift is -90°C

2

3

Butterworth

Chebyschev

-----2-

2

--2---1-

Frequency at which Gv = -3dB

Frequency at which the amplitude response

-----2-

2

--2---1-

passes through specified max. ripple band and

enters the stop bank.

EXAMPLE

Figure 14 : 5th Order Low-pass Filter (Butterworth) with Unity Gain configuration

Ri

R1

Ci

C2

R2

C1

C4

R3

R4

C3

7/11

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