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APPLICATION INFORMATION

IN +

IN −

OUT

30 k

Ω

+

−

1/4 LP2901

IN +

IN −

100 k

Ω

1/4 LP2901

1/4 SN54/74LS00 or

1/4 SN54/74ALS1000A

+

−

12

3

OUT

Q2

Q1

Q3

LP2901-Q1

LOW-POWER QUAD DIFFERENTIAL COMPARATOR

SLCS148 – SEPTEMBER 2005

Figure 1 shows the basic configuration for using the LP2901 comparator. Figure 2 shows the diagram for using it

as a CMOS driver.

Figure 1. Basic Comparator

Figure 2. CMOS Driver

All pins of any unused comparators should be grounded. The bias network of the 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.

to prevent the input voltages from going negative by more than –0.3 V. The output section has two distinct

modes of operation, the Darlington mode and the ground-emitter mode. This unique drive circuit permits the

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

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 typical.

Figure 3. Output-Section Schematic Diagram

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