TLV271Q1, TLV272Q1, TLV274Q1

FAMILY OF 550 µA/Ch 3MHz RAILTORAIL OUTPUT

OPERATIONAL AMPLIFIERS

SGLS275 − OCTOBER 2004

13

POST OFFICE BOX 655303

APPLICATION INFORMATION

offset voltage

the corresponding gains. The following schematic and formula can be used to calculate the output offset

voltage:

V

OO +

V

IO

1

)

R

F

R

G

" I

IB

)

R

S

1

)

R

F

R

G

" I

IB–

R

F

+

−

VI

+

RG

RS

RF

IIB−

VO

IIB+

Figure 26. Output Offset Voltage Model

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 27).

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 27. 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 the 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 28. 2-Pole Low-Pass Sallen-Key Filter