LED DRIVER
The LMV321/LMV358/LMV324 can be used to drive an LED
as shown in Figure 23.
10006084
FIGURE 23. LED Driver
COMPARATOR WITH HYSTERESIS
The LMV321/LMV358/LMV324 can be used as a low power
comparator. Figure 24 shows a comparator with hysteresis.
The hysteresis is determined by the ratio of the two resistors.
10006080
FIGURE 20. Fixed Current Source
High Compliance Current Sink
VTH+ = VREF/(1+R 1/R2)+VOH/(1+R2/R1)
VTH− = VREF/(1+R 1/R2)+VOL/(1+R2/R1)
VH = (VOH−VOL)/(1+R 2/R1)
A current sink circuit is shown in Figure 21. The circuit re-
quires only one resistor (RE) and supplies an output current
which is directly proportional to this resistor value.
where
VTH+: Positive Threshold Voltage
VTH−: Negative Threshold Voltage
VOH: Output Voltage at High
VOL: Output Voltage at Low
VH: Hysteresis Voltage
Since LMV321/LMV358/LMV324 have rail-to-rail output, the
(VOH−VOL) is equal to VS, which is the supply voltage.
VH = VS/(1+R2/R1)
The differential voltage at the input of the op amp should not
exceed the specified absolute maximum ratings. For real
comparators that are much faster, we recommend you use
National's LMV331/LMV93/LMV339, which are single, dual
and quad general purpose comparators for low voltage oper-
ation.
10006082
FIGURE 21. High Compliance Current Sink
POWER AMPLIFIER
A power amplifier is illustrated in Figure 22. This circuit can
provide a higher output current because a transistor follower
is added to the output of the op amp.
10006078
FIGURE 24. Comparator with Hysteresis
10006079
FIGURE 22. Power Amplifier
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