LT1490/LT1491
Dual and Quad
Micropower Rail-to-Rail
Input and Output Op Amps
FEATURES
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DESCRIPTION
The dual LT
®
1490 and quad LT1491 op amps operate on all
single and split supplies with a total voltage of 2V to 44V
drawing only 40µA of quiescent current per amplifier. These
amplifiers are reverse supply protected; they draw no current
for reverse supply up to 18V. The input range of the LT1490/
LT1491 includes both supplies and the output swings to both
supplies. Unlike most micropower op amps, the LT1490/
LT1491 can drive heavy loads; their rail-to-rail outputs drive
20mA. The LT1490/LT1491 are unity-gain stable and drive all
capacitive loads up to 10,000pF when optional 0.22µF and
150Ω compensation is used.
The LT1490/LT1491 have a unique input stage that oper-
ates and remains high impedance when above the positive
supply. The inputs take 44V both differential and common
mode even when operating on a 3V supply. Built-in resis-
tors protect the inputs for faults below the negative supply
up to 22V. There is no phase reversal of the output for inputs
22V below V
–
or 44V above V
–
, independent of V
+
.
The LT1490 dual op amp is available in the 8-pin SO and
PDIP packages. The quad LT1491 is available in the 14-pin
SO and PDIP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Rail-to-Rail Input and Output
Single Supply Input Range: – 0.4V to 44V
Micropower: 50µA/Amplifier Max
Specified on 3V, 5V and
±15V
Supplies
High Output Current: 20mA
Output Drives 10,000pF with Output Compensation
Reverse Battery Protection to 18V
No Supply Sequencing Problems
High Voltage Gain: 1500V/mV
High CMRR: 98dB
No Phase Reversal
Gain Bandwidth Product: 200kHz
APPLICATIONS
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Battery- or Solar-Powered Systems
Portable Instrumentation
Sensor Conditioning
Supply Current Sensing
Battery Monitoring
Micropower Active Filters
4mA to 20mA Transmitters
TYPICAL APPLICATION
CHARGER
VOLTAGE
R
S
0.2Ω
I
BATT
RA
2k
R
A
'
2k
Battery Monitor
Q1
2N3904
+
–
A
1/4 LT1491
–
C
1/4 LT1491
+
R
B
2k
R
B
'
2k
LOAD
+
–
Q2
2N3904
B
1/4 LT1491
LOGIC HIGH (5V) = CHARGING
LOGIC LOW (0V) = DISCHARGING
+
V
BATT
= 12V
S1
R
G
10k
10k
D
1/4 LT1491
+
–
90.9k
I
BATT
=
V
OUT
V
=
OUT
AMPS
(R
S
)(R
G
/R
A
)(GAIN) GAIN
S1 = OPEN, GAIN = 1
S1 = CLOSED, GAIN = 10
R
A
= R
B
V
S
= 5V, 0V
U
U
U
LOGIC
V
OUT
1490/91 TA01
1
LINER [ LINEAR TECHNOLOGY ]
