LT1113_15 Datasheet, PDF (13/16 Pages) Linear Technology – Dual Low Noise, Precision, JFET Input Op Amp

LT1113
TYPICAL APPLICATI S
Accelerometer Amplifier with DC Servo
ACCELEROMETER
B & K MODEL 4381
OR EQUIVALENT
R1
100M
C1
1250pF
R2
18k
R3 C2
2k 2µF
6
7
5V TO 15V
2– 8
1/2 LT1113
5
1
1/2 LT1113
3+
4
–5V TO –15V
R4
20M
R5
20M
C3
2µF
R4C2 = R5C3 > R1 (1 + R2/R3) C1
OUTPUT = 0.8mV/pC* = 8.0mV/g**
DC OUTPUT ≤ 2.7mV
OUTPUT NOISE = 6nV/√Hz AT 1kHz
*PICOCOULOMBS
**g = EARTH’S GRAVITATIONAL CONSTANT
OUTPUT
1113 • TA03
Paralleling Amplifiers to Reduce Voltage Noise
3₊
A1
1
1k
1/2 LT1113
2_–
51Ω
1k
10k
3₊
A2
1
1k
1/2 LT1113
2_–
51Ω
1k
15V
6– 8
7
1/2 LT1113
5+
4
OUTPUT
15V
–15V
5₊ 8
An
7
1k
1/2 LT1113
6_–
4
1. ASSUME VOLTAGE NOISE OF LT1113 AND 51Ω SOURCE RESISTOR = 4.6nV/√Hz
51Ω
–15V
1k
2. GAIN WITH n LT1113s IN PARALLEL = n • 200
3. OUTPUT NOISE = √n • 200 • 4.6nV/√Hz
4. INPUT REFERRED NOISE = ^{OUTPUT NOISE} = ^4.6
n • 200 √n
nV/√Hz
5. NOISE CURRENT AT INPUT INCREASES √n TIMES
6. IF n = 5, GAIN = 1000, BANDWIDTH = 1MHz, RMS NOISE, DC TO 1MHz = ^9µV = 4µV
√5
1113 • TA04
1113fb
13