|LP339||LOW-POWER QUAD DIFFERENTIAL COMPARATORS|
|LP339 Datasheet PDF : 13 Pages |
LP239, LP339, LP2901
LOWĆPOWER QUAD DIFFERENTIAL COMPARATORS
SLCS004B − OCTOBER 1987 − REVISED SEPTEMBER 2004
The LP239 is obsolete
and is no longer supplied.
Figure 1 shows the basic configuration for using the LP239, LP339, or LP2901 comparator. Figure 2 shows the
diagram for using one of these comparators as a CMOS driver.
1/4 LP239, LP339,
1/4 LP239, LP339,
1/4 SN54/74LS00 or
Figure 1. Basic Comparator
Figure 2. CMOS Driver
All pins of any unused comparators should be grounded. The bias network of the LP239, LP339, and LP2901
establishes a drain current that is independent of the magnitude of the power-supply voltage over the range of
2 V to 30 V. It usually is necessary to use a bypass capacitor across the power supply line.
The differential input voltage may be larger than VCC without damaging the device. Protection should be
provided to prevent the input voltages from going negative by more than −0.3 V. The output section has two
distinct modes of operation: a Darlington mode and ground-emitter mode. This unique drive circuit permits the
device to sink 30 mA at VO = 2 V in the Darlington mode and 700 µA at VO = 0.4 V in the ground-emitter mode.
Figure 3 is a simplified schematic diagram of the output section. The output section is configured in a Darlington
connection (ignoring Q3). If the output voltage is held high enough (above 1 V), Q1 is not saturated and the
output current is limited only by the product of the hFE of Q1, the hFE of Q2, and I1 and the 60-Ω saturation
resistance of Q2. The devices are capable of driving LEDs, relays, etc. in this mode while maintaining an
ultra-low power-supply current of 60 µA, typically.
I1 = 6 µA
Figure 3. Output-Section Schematic Diagram
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