The LP239 is obsolete

and is no longer supplied.

LP239, LP339, LP2901

LOW POWER QUAD DIFFERENTIAL COMPARATORS

SLCS004B − OCTOBER 1987 − REVISED SEPTEMBER 2004

4

POST OFFICE BOX 655303

APPLICATION INFORMATION

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.

Figure 1. Basic Comparator

IN +

IN −

OUT

30 k

Ω

+

−

VCC

1/4 LP239, LP339,

or LP2901

Figure 2. CMOS Driver

IN +

IN −

100 k

Ω

1/4 LP239, LP339,

or LP2901

1/4 SN54/74LS00 or

1/4 SN54/74ALS1000A

VCC

+

−

12

3

OUT

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.

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

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, typically.

VCC

VO

Q2

Q1

Q3

I1 = 6

µA

Figure 3. Output-Section Schematic Diagram