LT1028 Datasheet, PDF (14/20 Pages) Linear Technology – Ultra Low Noise Precision High Speed Op Amps

LT1028/LT1128
APPLICATI S 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-
10pF
10k
1.1k
–
LT1028
+
50Ω
1028/1128 AI11
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.
TYPICAL APPLICATI
Strain Gauge Signal Conditioner with Bridge Excitation
Low Noise Voltage Regulator
15V
LT1021-5
3₊ 7
5.0V
LT1128
2_{– 4}
–15V
350Ω
BRIDGE
15V
3_– 7
6
LT1028
2_{+ 4}
330Ω
6
REFERENCE
OUTPUT
15V
3_– 7
301k*
10k
ZERO
TRIM
LT1028
2₊
4
–15V
*RN60C FILM RESISTORS
330Ω
28V
1k
LT1021-10
+
6
0V TO 10V
OUTPUT
LT1028
–
1µF 30.1k*
5k
GAIN
TRIM
49.9Ω*
28V 10
+
LT317A
10
121Ω
2.3k
PROVIDES PRE-REG
AND CURRENT
LIMITING
330Ω
2N6387
1000pF
20V OUTPUT
2k
2k
1028/1128 TA04
–15V
THE LT1028’s NOISE CONTRIBUTION IS NEGLIGIBLE
COMPARED TO THE BRIDGE NOISE.
1028/1128 TA05
14