
LT1991
7
1991fb
BLOCK DIAGRA
PIU
P1 (Pin 1):
Noninverting Gain-of-1 input. Connects a 450k
internal resistor to the op amp’s noninverting input.
P3 (Pin 2):
Noninverting Gain-of-3 input. Connects a 150k
internal resistor to the op amp’s noninverting input.
P9 (Pin 3):
Noninverting Gain-of-9 input. Connects a 50k
internal resistor to the op amp’s noninverting input.
V
EE
(Pin 4):
Negative Power Supply. Can be either ground
(in single supply applications), or a negative voltage (in
split supply applications).
REF (Pin 5):
Reference Input. Sets the output level when
difference between inputs is zero. Connects a 450k inter-
nal resistor to the op amp’s noninverting input.
OUT (Pin 6):
Output. V
OUT
= V
REF
+ 1 (V
P1
– V
M1
) + 3
(V
P3
– V
M3
) + 9 (V
P9
– V
M9
).
V
CC
(Pin 7):
Positive Power Supply. Can be anything from
2.7V to 36V above the V
EE
voltage.
M9 (Pin 8):
Inverting Gain-of-9 input. Connects a 50k
internal resistor to the op amp’s inverting input.
M3 (Pin 9):
Inverting Gain-of-3 input. Connects a 150k
internal resistor to the op amp’s inverting input.
M1 (Pin 10):
Inverting Gain-of-1 input. Connects a 450k
internal resistor to the op amp’s inverting input.
Exposed Pad:
Must be soldered to PCB.
(Difference Amplifier Configuration)
Small Signal Transient Response
Small Signal Transient Response
Small Signal Transient Response
TYPICAL PERFOR U
50mV/DIV
5
μ
s/DIV
GAIN = 1
1991 G18
50mV/DIV
5
μ
s/DIV
1991 G19
GAIN = 3
50mV/DIV
5
μ
s/DIV
GAIN = 9
1991 G20
LT1991
1991 BD
9
8
2
3
4
5
7
6
10
1
M1
M3
M9
P1
P3
P9
V
CC
V
EE
OUT
REF
50k
50k
150k
150k
450k
450k
450k
450k
INM
INP
OUT
4pF
4pF