Datasheet

V
A2
=
V
CC
(R
2
||R
3
)
R
1
+ (R
2
||R
3)
V
A1
=
V
CC
.R
2
R
2
+ R
1
||R
3
C
1
R
4
V
O
R
2
R
3
R
1
V
A
+
-
V
C
V
+
0
V
+
LPV7215
www.ti.com SNOSAI6I –SEPTEMBER 2005–REVISED APRIL 2013
Figure 40. IR Receiver
SQUARE WAVE GENERATOR
A typical application for a comparator is as a square wave oscillator. The circuit in Figure 41 generates a square
wave whose period is set by the RC time constant of the capacitor C
1
and resistor R
4
. The maximum frequency
is limited by the large signal propagation delay of the comparator and by the capacitive loading at the output,
which limits the output slew rate.
Figure 41. Square Wave Oscillator
Consider the output of Figure 41 to be high to analyze the circuit. That implies that the inverted input (V
C
) is
lower than the non-inverting input (V
A
). This causes the C
1
to be charged through R
4
, and the voltage V
C
increases until it is equal to the non-inverting input. The value of V
A
at this point is
If R
1
= R
2
= R
3
then V
A1
= 2V
CC
/3
At this point the comparator switches pulling down the output to the negative rail. The value of V
A
at this point is
If R
1
= R
2
= R
3
then V
A2
= V
CC
/3
Copyright © 2005–2013, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LPV7215