TLV2371EP, TLV2372EP, TLV2374EP

FAMILY OF 550 µA/Ch 3MHz RAILTORAIL INPUT/OUTPUT

OPERATIONAL AMPLIFIERS

SGLS306A − APRIL 2005 − REVISED APRIL 2006

14

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251−1443

APPLICATION INFORMATION

general configurations

When receiving low-level signals, limiting the bandwidth of the incoming signals into the system is often

required. The simplest way to accomplish this is to place an RC filter at the noninverting terminal of the amplifier

(see Figure 31).

VI

VO

C1

+

−

RG

RF

R1

f

–3dB +

1

2

pR1C1

V

O

V

I

+

1

)

R

F

R

G

1

1

) sR1C1

VDD/2

Figure 31. Single-Pole Low-Pass Filter

If even more attenuation is needed, a multiple pole filter is required. The Sallen-Key filter can be used for this

task. For best results, the amplifier should have a bandwidth that is 8 to 10 times the filter frequency bandwidth.

Failure to do this can result in phase shift of the amplifier.

VI

C2

R2

R1

C1

RF

RG

R1 = R2 = R

C1 = C2 = C

Q = Peaking Factor

(Butterworth Q = 0.707)

(

=

1

Q

2 −

)

RG

RF

_

+

f

–3dB +

1

2

pRC

VDD/2

Figure 32. 2-Pole Low-Pass Sallen-Key Filter