LM339, LM239, LM2901, LM2901V, NCV2901, MC3302
http://onsemi.com
6
APPLICATIONS INFORMATION
These quad 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 itself
during output transitions (V
OL
to V
OH
). To alleviate this
situation input resistors < 10 k
should be used. The
addition of positive feedback (< 10 mV) is also
recommended. It is good design practice to ground all
unused input pins.
Differential input voltages may be larger than supply
voltages without damaging the comparator’s inputs.
Voltages more negative than −300 mV should not be used.
10
Figure 9. Zero Crossing Detector
(Single Supply)
Figure 10. Zero Crossing Detector
(Split Supplies)
V
in(min)
≈
0.4 V peak for 1% phase distortion (
).
D1 prevents input from going negative by more than 0.6 V.
R1 + R2 = R3
R3
≤
R5
for small error in zero crossing
V
in
10 k
D1
R1
8.2 k
6.8 k
R2
15 k
R3
+15 V
V
CC
10 k
V
in
V
EE
V
in
V
in(min)
V
CC
V
O
V
EE
10 M
R5
220 k
R4
220 k
V
O
V
O
+
