9

LT1077

1077fa

the most representative for battery powered micropower

circuits. Offset voltage is internally trimmed to a minimum

value at these supply voltages. When 9V or 3V batteries,

or ±2.5V dual supplies are used, bias and offset current

changes will be minimal. Offset voltage changes will be

just a few microvolts as given by the PSRR and CMRR

specifications. For example, if PSRR = 114dB ( = 2µV/V),

at 9V the offset voltage change will be 8µV. Similarly,

CMRR = 110dB (3µV/V).

A full set of specifications is also provided at ±15V supply

voltages for comparison with other devices and for

completeness.

The LT1077 is pin compatible to, and directly replaces,

such precision op amps as the OP-07, OP-77, AD7O7 and

LT1001 with 30 to 60 times savings in supply current. The

LT1077 is also a direct plug-in replacement for LT1012

and OP-97 devices with 10 times lower dissipation.

Compatibility includes externally nulling the offset

voltage, as all of the devices above are trimmed with

a potentiometer between Pins 1 and 8 and the wiper

The LT1077 replaces and upgrades such micropower op

amps as the OP-20, LM4250, and OP-90, provided that the

external nulling circuitry (and set resistor in the case of the

LM4250) are removed. Since the offset voltage of the

LT1077 is extremely low, nulling will be unnecessary in

most applications.

Single Supply Operation

The LT1077 is fully specified for single supply operation,

(i.e., when the negative supply is 0V). Input common

mode range goes below ground and the output swings

within a few millivolts of ground while sinking current. All

competing micropower op amps either cannot swing to

within 600mV of ground (OP-20, OP-220, OP-420) or

need a pull-down resistor connected to the output to

swing to ground (OP-90, OP-290, OP-490, HA5141/42/

44). This difference is critical because in many applica-

tions these competing devices cannot be operated as

micropower op amps and swing to ground simultaneously.

Consider the difference amplifiers shown in Typical

Applications as an example. When the common mode

signal is high and the output low, the amplifier has to sink

current. In the gain of 10 circuit, the competing devices

require a 30k pull-down resistor at the output to handle the

specified signals. (The LT1077 does not need pull-down

TYPICAL PERFOR A CE CHARACTERISTICS

Common Mode Rejection Ratio

vs Frequency

Power Supply Rejection Ratio

vs Frequency

FREQUENCY (Hz)

10

0

20

40

60

80

100

120

100

1k

10k

100k

LT1077 • TPC28

1M

FREQUENCY (Hz)

0.1

80

100

120

100

10k

LT1077 • TPC29

60

40

110

1k

100k

20

0

POSITIVE

SUPPLY

NEGATIVE

SUPPLY

APPLICATIO S I FOR ATIO