LT1996 Linear Technology, LT1996 Datasheet - Page 8

• Manufacturer Part Number: LT1996
• Description: 100uA Gain Selectable Amplifier
• Manufacturer: Linear Technology

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BLOCK DIAGRA
APPLICATIO S I FOR ATIO
LT1996
Introduction
The LT1996 may be the last op amp you ever have to stock.
Because it provides you with several precision matched
resistors, you can easily configure it into several different
classical gain circuits without adding external compo-
nents. The several pages of simple circuits in this data
sheet demonstrate just how easy the LT1996 is to use. It
can be configured into difference amplifiers, as well as into
inverting and noninverting single ended amplifiers. The
fact that the resistors and op amp are provided together in
such a small package will often save you board space and
reduce complexity for easy probing.
The Op Amp
The op amp internal to the LT1996 is a precision device
with 15µV typical offset voltage and 3nA input bias cur-
rent. The input offset current is extremely low, so match-
ing the source resistance seen by the op amp inputs will
provide for the best output accuracy. The op amp inputs
are not rail-to-rail, but extend to within 1.2V of V
8
4
U
W
U
W
10
1
P9
M9
9
2
P27
M27
U
CC
450k/9
450k/9
8
3
450k/27
450k/27
and 1V
450k/81
450k/81
P81
M81
of V
will function rail-to-rail because of effective attenuation to
the +input. The output is truly rail-to-rail, getting to within
40mV of the supply rails. The gain bandwidth product of
the op amp is about 560kHz. In noise gains of 2 or more,
it is stable into capacitive loads up to 500pF. In noise gains
below 2, it is stable into capacitive loads up to 100pF.
The Resistors
The resistors internal to the LT1996 are very well matched
SiChrome based elements protected with barrier metal.
Although their absolute tolerance is fairly poor (±30%),
their matching is to within 0.05%. This allows the chip to
achieve a CMRR of 80dB, and gain errors within 0.05%.
The resistor values are (450k/9), (450k/27), (450k/81)
and 450k, connected to each of the inputs. The resistors
have power limitations of 1watt for the 450k and (450k/81)
resistors, 0.3watt for the (450k/27) resistors and 0.5watt
for the (450k/9) resistors; however, in practice, power
dissipation will be limited well below these values by the
4pF
4pF
–
+
EE
. For many configurations though, the chip inputs
7
4
OUT
V
V
450k
EE
CC
450k
LT1996
6
5
OUT
REF
1996 BD
1996f