Datasheet

15
LT1215/LT1216
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
Comparator Applications
Sometimes it is desirable to use an op amp as a compara-
tor. When operating the LT1215/LT1216 on a single 3.3V
or 5V supply, the output interfaces directly with most TTL
and CMOS logic.
The response time of the LT1215/LT1216 is a strong
function of the amount of input overdrive as shown in the
4
2
0
100
0
5µs/DIV
V
S
= 5V 1215/16 AI01
R
L
= ∞
4
2
0
100
0
5µs/DIV
V
S
= 5V 1215/16 AI02
R
L
= ∞
LT1215 Comparator Response (+)
20mV, 10mV, 5mV, 2mV Overdrives
LT1215 Comparator Response (–)
20mV, 10mV, 5mV, 2mV Overdrives
W
I
SPL
II
F
ED S
W
A
CH
E
TI
C
following photos. These amplifiers are unity-gain stable
op amps and not fast comparators, therefore, the logic
being driven may oscillate due to the long transition time.
The output can be speeded up by adding 20mV or more of
hysteresis (positive feedback), but the offset is then a
function of the input direction.
INPUT (mV)
OUTPUT (V)
OUTPUT (V)
INPUT (mV)
C
I
Q5
Q10
C
F
R
F
I
7
I
8
C
O
V
–
C
M
BIAS
OUT
V
+
I
6
I
5
I
4
I
3
I
2
I
1
–IN
+IN
1215/16 SS
Q7
Q9
Q8
Q11
Q12
Q14
Q15
Q13
Q16
Q6
Q3
Q4
Q1
Q2