LT2079_15 Datasheet, PDF (12/16 Pages) Linear Technology – Micropower, Dual and Quad, Single Supply, Precision Op Amps

LT2078/LT 2079
APPLICATIONS INFORMATION
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, 70µV maximum offset voltage implies that mis-
match cannot be more than 140µV. 95dB (= 17.5µV/V)
CMRR means that worst-case CMRR match is 89dB
(= 35µV/V). However, Table 1 can be used to estimate the
expected matching performance at V_S = 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.
4
2
0
0
–100
V_S = 5V, 0V
200µs/DIV
LT2078/79 • F03
Figure 3. Comparator Rise Response
Time to 10mV, 5mV, 2mV Overdrives
4
2
0
100
0
V_S = 5V, 0V
200µs/DIV
LT2078/79 • F04
Figure 4. Comparator Fall Response
Time to 10mV, 5mV, 2mV Overdrives
TYPICAL APPLICATIONS
Micropower, 10ppm/°C, ±5V Reference
2M
LT1034BC-1.2
220k
9V
5V_OUT
1M
120k _{3 +} 8
1
1/2 LT2078
1M
6_–
2_–
4
–9V _510k
1/2 LT2078
510k _{5 +}
7
– 5.000V_OUT
LT2078/79 • TA03
1%
SUPPLY CURRENT = 9V BATTERY = 115µA
160k ^20k
1%
–9V BATTERY = 85µA
OUTPUT NOISE = 36µV_P-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
Gain of 10 Difference Amplifier
10M
1M
–IN
1M
+IN
3V
–
1/2 LT2078
+
OUTPUT
0.0035V TO 2.4V
LT2078/79 • TA04
BANDWIDTH= 20kHz
10M
OUTPUT OFFSET= 0.7mV
OUTPUT NOISE= 80µV_P-P (0.1Hz TO 10Hz)
260µV_RMS 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
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