TLV277xEP, TLV277xAEP

FAMILY OF 2.7V HIGHSLEW RATE RAILTORAIL OUTPUT

OPERATIONAL AMPLIFIERS WITH SHUTDOWN

SGLS317A − OCTOBER 2005 − REVISED SEPTEMBER 2007

27

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 60. 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 61).

VI

VO

C1

+

−

RG

RF

R1

f

–3dB +

1

2

pR1C1

V

O

V

I

+

1

)

R

F

R

G

1

1

) sR1C1

Figure 61. 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 eight to ten 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

Figure 62. Two Pole Low Pass Sallen Key Filter