12
LT2078/LT 2079
20789fa
APPLICATIONS INFORMATION
WU
U
4
VS = 5V, 0V
200
s/DIV
LT2078/79 F03
2
0
–100
INPUT
(mV)
OUTPUT
(V)
Figure 3. Comparator Rise Response
Time to 10mV, 5mV, 2mV Overdrives
VS = 5V, 0V
200
s/DIV
LT2078/79 F04
0
100
0
INPUT
(mV)
OUTPUT
(V)
4
2
Figure 4. Comparator Fall Response
Time to 10mV, 5mV, 2mV Overdrives
the individual characteristics of the two devices, the two
and three op amp instrumentation amplifier configura-
tions shown in this data sheet are examples. Matching
characteristics are not 100% tested on the LT2078/LT2079.
Some specifications are guaranteed by definition. For
example, 70
V maximum offset voltage implies that mis-
match cannot be more than 140
V. 95dB (= 17.5V/V)
CMRR means that worst-case CMRR match is 89dB
(= 35
V/V). However, Table 1 can be used to estimate the
expected matching performance at VS = 5V, 0V between
the two sides of the LT2078, and between amplifiers A and
D, and between amplifiers B and C of the LT2079.
Comparator Applications
The single supply operation of the LT2078/LT2079 and its
ability to swing close to ground while sinking current
lends itself to use as a precision comparator with TTL
compatible output.
TYPICAL APPLICATIONS
U
Micropower, 10ppm/
°C, ±5V Reference
Gain of 10 Difference Amplifier
+
–
1M
10M
OUTPUT
0.0035V TO 2.4V
1/2 LT2078
BANDWIDTH= 20kHz
OUTPUT OFFSET= 0.7mV
OUTPUT NOISE= 80
VP-P (0.1Hz TO 10Hz)
260
VRMS OVER FULL
BANDWIDTH
THE USEFULNESS OF DIFFERENCE AMPLIFIERS IS LIMITED BY THE FACT THAT
THE INPUT RESISTANCE IS EQUAL TO THE SOURCE RESISTANCE. THE PICOAMPERE
OFFSET CURRENT AND LOW CURRENT NOISE OF THE LT2078 ALLOWS THE USE OF
1M SOURCE RESISTORS WITHOUT DEGRADATION IN PERFORMANCE. IN ADDITION,
WITH MEGOHM RESISTORS MICROPOWER OPERATION CAN BE MAINTAINED
LT2078/79 TA04
–IN
+IN
10M
3V
–
+
–
2M
220k
120k
3
2
1
8
4
1/2 LT2078
9V
5VOUT
1M
6
5
7
LT1034BC-1.2
510k
1M
–5.000VOUT
–9V
510k
1%
20k
160k
1%
1/2 LT2078
SUPPLY CURRENT = 9V BATTERY = 115
A
–9V BATTERY = 85
A
OUTPUT NOISE = 36
VP-P, 0.1Hz TO 10Hz
THE LT2078 CONTRIBUTES LESS THAN 3% OF THE TOTAL OUTPUT NOISE AND
DRIFT WITH TIME AND TEMPERATURE. THE ACCURACY OF THE –5V OUTPUT
DEPENDS ON THE MATCHING OF THE TWO 1M RESISTORS
LT2078/79 TA03