LT1996 Linear Technology, LT1996 Datasheet - Page 11

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

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APPLICATIO S I FOR ATIO
suggested in Figure 1: raise V
some negative V
Likewise, from the lower common mode extreme, making
the negative input more negative will raise the output
voltage, limited by V
Again, the additional input range calculated here is only
available provided the other remaining constraint is not
violated, the maximum voltage allowed on the pin.
The Classical Noninverting Amplifier: High Input Z
Perhaps the most common op amp configuration is the
noninverting amplifier. Figure 4 shows the textbook
4
MIN V
(should be negative)
Figure 4. The LT1996 as a Classical Noninverting Op Amp
V
IN
CLASSICAL NONINVERTING OP AMP CONFIGURATION.
YOU PROVIDE THE RESISTORS.
MORE
CLASSICAL NONINVERTING OP AMP CONFIGURATION
IMPLEMENTED WITH LT1991. R
GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK
THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED R
WE PROVIDE YOU WITH <0.1% RESISTORS.
10
8
9
1
2
3
= (V
450k/81
450k/27
450k/27
450k/81
450k/9
450k/9
R
MORE
G
V
IN
REF
U
CC
.
– V
– 0.04V.
–
+
U
CC
450k
R
–
+
F
+ 0.04V) • R
REF
F
V
GAIN = 1 + R
450k
4pF
= 45k, R
4pF
4pF
4pF
OUT
, lower V
= GAIN • V
W
5
G
= 5.6k, GAIN = 9.1.
LT1996
F
/R
V
OUT
G
IN
G
EE
/R
6
, or provide
F
F
AND R
U
1996 F04
V
G
OUT
.
representation of the circuit on the top. The LT1996 is
shown on the bottom configured in a precision gain of 9.1.
One of the benefits of the noninverting op amp configura-
tion is that the input impedance is extremely high. The
LT1996 maintains this benefit. Given the finite number of
available feedback resistors in the LT1996, the number of
gain configurations is also finite. The complete list of such
Hi-Z input noninverting gain configurations is shown in
Table 1. Many of these are also represented in Figure 5 in
schematic form. Note that the P-side resistor inputs have
been connected so as to match the source impedance
seen by the internal op amp inputs. Note also that gain and
noise gain are identical, for optimal precision.
Table 1. Configuring the M Pins for Simple Noninverting Gains.
The P Inputs are driven as shown in the examples on the next
page
Gain
1.08
1.11
1.30
1.32
1.33
1.44
3.19
3.89
4.21
11.8
109
118
3.7
9.1
10
28
37
82
91
1
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Output
Output
Output
Output
Output
Output
M81
Float
Float
Float
Float
Float
M81, M27, M9 Connection
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Output
Output
Output
Output
Output
Output
Float
Float
Float
Float
Float
M27
LT1996
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Grounded
Output
Output
Output
Output
Output
Output
Float
Float
Float
Float
Float
M9
11
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