LT1028_15 Datasheet, PDF (17/28 Pages) Linear Technology – Ultralow Noise Precision High Speed Op Amps

Typical Applications
Paralleling Amplifiers to Reduce Voltage Noise
LT1028/LT1128
+
A1
1.5k
LT1028
–
7.5Ω
470Ω
+
A2
1.5k
LT1028
–
7.5Ω
470Ω
+
An
1.5k
LT1028
–
7.5Ω
470Ω
4.7k
–
LT1028
+
OUTPUT
1. ASSUME VOLTAGE NOISE OF LT1028 AND 7.5Ω SOURCE RESISTOR = 0.9nV/√Hz.
2. GAIN WITH n LT1028s IN PARALLEL = n • 200.
3. OUTPUT NOISE = √n • 200 • 0.9nV/√Hz.
4.
INPUT
REFERRED
NOISE
=
OUTPUT NOISE
n • 200
=
0.9
√n
nV/√Hz.
5. NOISE CURRENT AT INPUT INCREASES √n TIMES.
6. IF n = 5, GAIN = 1000, BANDWIDTH = 1MHz, RMS NOISE, DC TO 1MHz = ^2µV = 0.9µV.
√5
1028 TA05
For more information www.linear.com/LT1028
1028fc
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