LM393, LM393E, LM293, LM2903, LM2903E, LM2903V, NCV2903

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5

APPLICATIONS INFORMATION

These dual comparators feature high gain, wide

bandwidth characteristics. This gives the device oscillation

tendencies if the outputs are capacitively coupled to the

inputs via stray capacitance. This oscillation manifests

this situation, input resistors < 10 k

W should be used.

The addition of positive feedback (< 10 mV) is also

recommended. It is good design practice to ground all

unused pins.

Differential input voltages may be larger than supply

voltage without damaging the comparator’s inputs. Voltages

more negative than −0.3 V should not be used.

Figure 8. Zero Crossing Detector

(Single Supply)

Figure 9. Zero Crossing Detector

(Split Supply)

Figure 10. Free−Running Square−Wave Oscillator

Figure 11. Time Delay Generator

Figure 12. Comparator with Hysteresis

10

D1 prevents input from going negative by more than 0.6 V.

R1 + R2 = R3

R3

≤

R5

for small error in zero crossing.

10 k

D1

R1

8.2 k

6.8 k

R2

15 k

R3

+15 V

10 m

R5

220 k

R4

220 k

LM393

*

Q

10 k

DQ

Q

LM393

-

+

LM393

51 k

51 k

51 k

10 k

t

0

1.0 m

W

0.001

mF

-

+

LM393

0

0

0

t

``ON'' for t

where:

Dt = RC n (

)

R

C

LM393

-

+

R1

R2

R1 + R2

R1

t

+

-

LM393

)

*

)