Datasheet LT1792 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Low Noise, Precision, JFET Input Op Amp |
| Pages / Page | 12 / 10 — APPLICATI. S I FOR ATIO. Figure 5. TYPICAL APPLICATI. Accelerometer … |
| File Format / Size | PDF / 183 Kb |
| Document Language | English |
APPLICATI. S I FOR ATIO. Figure 5. TYPICAL APPLICATI. Accelerometer Amplifier with DC Servo
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LT1792
O U U W U APPLICATI S I FOR ATIO
also increases the parasitic gate capacitance, which if left CF unchecked, can result in increased overshoot and ring- ing. When the feedback around the op amp is resistive RF (RF), a pole will be created with RF, the source resistance and capacitance (RS, CS), and the amplifier input capaci- – tance (CIN = 27pF). In low gain configurations and with C OUTPUT R IN S and RF in the kilohm range (Figure 5), this pole can + R create excess phase shift and even oscillation. A small S CS capacitor (CF) in parallel with RF eliminates this problem. 1792 F05 With RS(CS + CIN) = RFCF, the effect of the feedback pole is completely removed.
Figure 5 O U TYPICAL APPLICATI S Accelerometer Amplifier with DC Servo
C1 1250pF R1 C2 R3 R2 100M 2µF 2k 18k R4 R4C2 = R5C3 > R1 (1 + R2/R3) C1 2 20M – OUTPUT = 0.8mV/pC* = 8.0mV/g** 6 DC OUTPUT ≤ 2.7mV LT1792 R5 OUTPUT NOISE = 6nV/√ Hz AT 1kHz + 3 20M 5V TO 15V *PICOCOULOMBS C3 **g = EARTH’S GRAVITATIONAL CONSTANT ACCELEROMETER 2 – 7 2µF B & K MODEL 4381 OR EQUIVALENT 6 LT1792 OUTPUT 1792 TA03 3 + 4 – 5V TO –15V
10Hz Fourth Order Chebyshev Lowpass Filter (0.01dB Ripple)
C1 R2 33nF 237k C3 R5 10nF 154k 15V R1 R3 237k 249k 2 – 7 V R4 R6 IN 154k 249k 6 2 – C2 LT1792 + 100nF 3 6 LT1792 VOUT C4 4 + 330nF 3 –15V 1792 TA06 TYPICAL OFFSET ≈ 0.8mV 1% TOLERANCES FOR VIN = 10VP-P, VOUT = –121dB AT f > 330Hz = – 6dB AT f = 16.3Hz LOWER RESISTOR VALUES WILL RESULT IN LOWER THERMAL NOISE AND LARGER CAPACITORS 10
O U U W U APPLICATI S I FOR ATIO
also increases the parasitic gate capacitance, which if left CF unchecked, can result in increased overshoot and ring- ing. When the feedback around the op amp is resistive RF (RF), a pole will be created with RF, the source resistance and capacitance (RS, CS), and the amplifier input capaci- – tance (CIN = 27pF). In low gain configurations and with C OUTPUT R IN S and RF in the kilohm range (Figure 5), this pole can + R create excess phase shift and even oscillation. A small S CS capacitor (CF) in parallel with RF eliminates this problem. 1792 F05 With RS(CS + CIN) = RFCF, the effect of the feedback pole is completely removed.
Figure 5 O U TYPICAL APPLICATI S Accelerometer Amplifier with DC Servo
C1 1250pF R1 C2 R3 R2 100M 2µF 2k 18k R4 R4C2 = R5C3 > R1 (1 + R2/R3) C1 2 20M – OUTPUT = 0.8mV/pC* = 8.0mV/g** 6 DC OUTPUT ≤ 2.7mV LT1792 R5 OUTPUT NOISE = 6nV/√ Hz AT 1kHz + 3 20M 5V TO 15V *PICOCOULOMBS C3 **g = EARTH’S GRAVITATIONAL CONSTANT ACCELEROMETER 2 – 7 2µF B & K MODEL 4381 OR EQUIVALENT 6 LT1792 OUTPUT 1792 TA03 3 + 4 – 5V TO –15V
10Hz Fourth Order Chebyshev Lowpass Filter (0.01dB Ripple)
C1 R2 33nF 237k C3 R5 10nF 154k 15V R1 R3 237k 249k 2 – 7 V R4 R6 IN 154k 249k 6 2 – C2 LT1792 + 100nF 3 6 LT1792 VOUT C4 4 + 330nF 3 –15V 1792 TA06 TYPICAL OFFSET ≈ 0.8mV 1% TOLERANCES FOR VIN = 10VP-P, VOUT = –121dB AT f > 330Hz = – 6dB AT f = 16.3Hz LOWER RESISTOR VALUES WILL RESULT IN LOWER THERMAL NOISE AND LARGER CAPACITORS 10
