Datasheet

14
LT1028/LT1128
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
If C
F
is only used to cut noise bandwidth, a similar effect
can be achieved using the over-compensation terminal.
The Gain, Phase plot also shows that phase margin is
about 45° at gain of 10 (20dB). The following configura-
tion has a high (70%) overshoot without the 10pF
capacitor because of additional phase shift caused by the
feedback resistor – input capacitance pole. The presence
of the 10pF capacitor cancels this pole and reduces
overshoot to 5%.
Over-Compensation
The LT1028/LT1128 are equipped with a frequency over-
compensation terminal (pin 5). A capacitor connected
between pin 5 and the output will reduce noise bandwidth.
Details are shown on the Slew Rate, Gain-Bandwidth
Product vs Over-Compensation Capacitor plot. An addi-
tional benefit is increased capacitive load handling capa-
bility.
1028/1128 AI11
10pF
10k
50
1.1k
+
LT1028
U
A
O
PP
L
IC
AT
ITY
P
I
CA
L
Strain Gauge Signal Conditioner with Bridge Excitation
Low Noise Voltage Regulator
1028/1128 TA05
1µF
REFERENCE
OUTPUT
+
LT1128
30.1k*
49.9*
15V
330
10k
ZERO
TRIM
5.0V
301k*
LT1021-5
0V TO 10V
OUTPUT
3
2
7
6
4
350Ω
BRIDGE
–15V
15V
15V
LT1028
+
3
2
7
6
4
–15V
LT1028
+
3
2
7
6
4
–15V
5k
GAIN
TRIM
330
*RN60C FILM RESISTORS
THE LT1028’s NOISE CONTRIBUTION IS NEGLIGIBLE
COMPARED TO THE BRIDGE NOISE.
1028/1128 TA04
10
2k
20V OUTPUT
+
LT1028
2.3k
PROVIDES PRE-REG
AND CURRENT
LIMITING
10
+
28V
121
2k
330
1000pF
1k
28V
LT317A
LT1021-10
2N6387