12

LT2078/LT 2079

4

200

µs/DIV

LT2078/79 • F03

2

0

0

–100

Figure 3. Comparator Rise Response

Time to 10mV, 5mV, 2mV Overdrives

200

µs/DIV

LT2078/79 • F04

0

100

0

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

µV maximum offset voltage implies that mis-

match cannot be more than 140

µV. 95dB (= 17.5µV/V)

CMRR means that worst-case CMRR match is 89dB

(= 35

µV/V). However, Table 1 can be used to estimate the

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.

Micropower, 10ppm/

°C, ±5V Reference

Gain of 10 Difference Amplifier

+

–

1M

1M

10M

OUTPUT

0.0035V TO 2.4V

1/2 LT2078

BANDWIDTH= 20kHz

OUTPUT OFFSET= 0.7mV

OUTPUT NOISE= 80

260

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

1M

6

5

7

LT1034BC-1.2

510k

1M

–9V

510k

1%

20k

160k

1%

1/2 LT2078

SUPPLY CURRENT = 9V BATTERY = 115

µA

–9V BATTERY = 85

µA

OUTPUT NOISE = 36

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