lmv358-mda National Semiconductor Corporation, lmv358-mda Datasheet - Page 14

• Manufacturer Part Number: lmv358-mda
• Description: General Purpose, Low Voltage, Rail-to-rail Output Operational Amplifiers
• Manufacturer: National Semiconductor Corporation

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In Figure 3 , the isolation resistor R
C
margin to the overall system. The desired performance de-
pends on the value of R
the more stable V
of Figure 3 using 620Ω for R
The circuit in Figure 5 is an improvement to the one in Figure
3 because it provides DC accuracy as well as AC stability. If
there were a load resistor in Figure 3, the output would be
voltage divided by R
ure 5, R
techniques to connect V
ing the value of R
LMV358/LMV324. C
of phase margin by feeding the high frequency component of
the output signal back to the amplifier's inverting input, there-
by preserving phase margin in the overall feedback loop.
Increased capacitive drive is possible by increasing the value
of C
FIGURE 5. Indirectly Driving A Capacitive Load with DC
L
FIGURE 4. Pulse Response of the LMV324 Circuit in
form a pole to increase stability by adding more phase
F
. This in turn will slow down the pulse response.
F
provides the DC accuracy by using feed-forward
F
OUT
due to the input bias current of theLMV321/
ISO
F
will be. Figure 4 is an output waveform
and R
ISO
and the load resistor. Instead, in Fig-
IN
Accuracy
. The bigger the R
Figure 3
to R
ISO
ISO
L
. Caution is needed in choos-
and 510 pF for C
serve to counteract the loss
ISO
and the load capacitor
ISO
10006005
resistor value,
L.
10006099
.
14
INPUT BIAS CURRENT CANCELLATION
The LMV321/LMV358/LMV324 family has a bipolar input
stage. The typical input bias current of LMV321/LMV358/
LMV324 is 15 nA with 5V supply. Thus a 100 kΩ input resistor
will cause 1.5 mV of error voltage. By balancing the resistor
values at both inverting and non-inverting inputs, the error
caused by the amplifier's input bias current will be reduced.
The circuit in Figure 6 shows how to cancel the error caused
by input bias current.
TYPICAL SINGLE-SUPPLY APPLICATION CIRCUITS
Difference Amplifier
The difference amplifier allows the subtraction of two voltages
or, as a special case, the cancellation of a signal common to
two inputs. It is useful as a computational amplifier, in making
a differential to single-ended conversion or in rejecting a com-
mon mode signal.
FIGURE 6. Cancelling the Error Caused by Input Bias
FIGURE 7. Difference Amplifier
Current
10006006
10006007
10006019