LT1126AM Linear Technology, LT1126AM Datasheet - Page 6

• Manufacturer Part Number: LT1126AM
• Description: Dual/Quad Decompensated Low Noise/ High Speed Precision Op Amps
• Manufacturer: Linear Technology

LT1126/LT1127
A
Matching Specifications
In many applications the performance of a system de-
pends on the matching between two op amps, rather than
the individual characteristics of the two devices. The three
op amp instrumentation amplifier configuration shown in
this data sheet is an example. Matching characteristics are
not 100% tested on the LT1126/LT1127.
Some specifications are guaranteed by definition. For
example, 70 V maximum offset voltage implies that mis-
match cannot be more than 140 V. 112dB (= 2.5 V/V)
CMRR means that worst case CMRR match is 106dB
(5 V/V). However, the following table can be used to
estimate the expected matching performance between the
two sides of the LT1126, and between amplifiers A and D,
and between amplifiers B and C of the LT1127.
Expected Match
PARAMETER
V
Temperature Coefficient Match
Average Non-Inverting I
Match of Non-Inverting I
CMRR Match
PSRR Match
6
TYPICAL
THE HIGH GAIN AND WIDE BANDWIDTH OF THE LT1126/LT1127 IS USEFUL IN LOW FREQUENCY HIGH CLOSED
LOOP GAIN AMPLIFIER APPLICATIONS. A TYPICAL PRECISION OP AMP MAY HAVE AN OPEN LOOP GAIN OF ONE
MILLION WITH 500kHz BANDWIDTH. AS THE GAIN ERROR PLOT SHOWS, THIS DEVICE IS CAPABLE OF 0.1%
AMPLIFYING ACCURACY UP TO 0.3Hz ONLY. EVEN INSTRUMENTATION RANGE SIGNALS CAN VARY AT A FASTER
RATE. THE LT1126/LT1127 “GAIN PRECISION — BANDWIDTH PRODUCT” IS 330 TIMES HIGHER, AS SHOWN.
OS
PPLICATI
Match, V
OS
Gain 1000 Amplifier with 0.01% Accuracy, DC to 5Hz
A
O
PPLICATI
LT1126
LT1127
B
B
U
365
1%
S
INPUT
I FOR ATIO
U
340k
1%
50% YIELD
O
–
+
LT1126
0.35
126
127
20
30
U
6
7
+15V
–15V
15k
5%
W
S
LT1126AM/AC
LT1127AM/AC
TRIM
RN60C FILM RESISTORS
20k
U
98% YIELD
OUTPUT
110
150
115
118
1.0
18
22
High Speed Operation
When the feedback around the op amp is resistive (R
pole will be created with R
capacitance (R
(C
with R
excess phase shift and even oscillation. A small capacitor
(C
R
completely removed.
S
IN
F
) in parallel with R
(C
S
S
LT1126 • TA03
2pF). In low closed loop gain configurations and
+ C
and R
50% YIELD
R
S
IN
123
127
0.5
30
50
) = R
7
8
F
S
, C
in the kilohm range, this pole can create
C
S
F
S
LT1126M/C
LT1127M/C
C
), and the amplifier input capacitance
F
0.001
, the effect of the feedback pole is
0.01
1.0
0.1
F
–
+
0.1
C
eliminates this problem. With
F
PRECISION
F
TYPICAL
C
, the source resistance and
98% YIELD
OP AMP
IN
Closed Loop Gain = 1000
Gain Error vs Frequency
GAIN ERROR =
130
180
112
114
1.5
R
25
30
F
FREQUENCY (Hz)
1
CLOSED LOOP GAIN
OPEN LOOP GAIN
LT1126 • TA02
OUTPUT
LT1126/LT1127
10
LT1126 • TA04
UNITS
F
V/ C
), a
100
nA
nA
dB
dB
V
V