Datasheet

TLV2381
TLV2382
SLOS377A – SEPTEMBER 2001– REVISED JULY 2003
9
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APPLICATION INFORMATION
offset voltage
The output offset voltage (V
OO
) is the sum of the input offset voltage (V
IO
) and both input bias currents (I
IB
) times 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
+
–
V
I
+
R
G
R
S
R
F
I
IB–
V
O
I
IB+
Figure 25. 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 26).
V
I
V
O
C1
+
–
R
G
R
F
R1
f
–3dB
1
2 R1C1
V
O
V
I
1
R
F
R
G
1
1 sR1C1
V
DD
/2
Figure 26. 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.
V
I
C2
R2R1
C1
R
F
R
G
R1 = R2 = R
C1 = C2 = C
Q = Peaking Factor
(Butterworth Q = 0.707)
(
=
1
Q
2 –
)
R
G
R
F
_
+
f
–3dB
1
2 RC
V
DD
/2
Figure 27. 2-Pole Low-Pass Sallen-Key Filter