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SPP FIELDS Preamp Power Requirements

This document outlines the power requirements and performance characteristics necessary for designing preamplifiers, focusing on noise performance, bandwidth, and dynamic range. It details the expected noise figures across frequency ranges (DC to 3 MHz), bandwidth specifications for low, medium, and high frequencies, and how power influences these parameters. The text also discusses practical amplifier choices, power dissipation metrics, and realistic power supply expectations essential for achieving optimal preamp performance in various applications.

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SPP FIELDS Preamp Power Requirements

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  1. SPP FIELDS PreampPower Requirements 01DEC2012 D. Seitz

  2. Noise + BW + Dynamic Range Noise • DC to 10 kHz, TBD nV/√Hz • 10 kHz to 700 kHz, 10 nV/√Hz • 700 kHz to 3 MHz, 3 nV/√Hz • Bandwidth • LF: DC - 64kHz; SR ≥ 4V/µs • MF: 2kHz – 1MHz; SR ≥ 60V/µs • HF: 2kHz – 20MHz; SR ≥ 1200V/µs • Dynamic Range • ±10V at LF in, x1 Gain • ±10V at MF in, x1 Gain • ±1V at HF in, x10 Gain

  3. Some General Principles • Lower Noise = Higher Power • Higher BW = Higher Power • Larger Voltage Swings = Higher Power We sort of want Everything. What will it cost? POWER

  4. FETs 60mW AD8001 150mW 44mW 490mW AD844 225mW OPA602 90mW >1 W!! Termination power Probably unrealistic – but what is realistic?

  5. FETs 60mW AD8001 150mW 44mW 490mW AD844 225mW OPA602 90mW 0.525 W AC coupled terminations, ignored Non-flat response Freq? Ampl?

  6. FETs 60mW AD8001 150mW 44mW 490mW AD8001 150mW OPA602 90mW 0.45 W AC coupled terminations, ignored MF  ±5V

  7. FETs 20mW AD8001 50mW +5V 44mW -5V 490mW AD8001 50mW OPA602 90mW +5V -5V 0.21 W AC coupled terminations, ignored All HF, MF ±15V  ±5V

  8. HF, MF Power Some typical op amp choices • AD844current feedback op amp • 60MHz GBW; 20MHz FPBW @ 20Vpp into 100Ω; 1200V/µs • 2nV/√Hz @ 1kHz • 225mW @ ±15Vs; 75mW @±5Vs • 100 krads - needsshielding (300 kradreq) • AD8001currentfeedbackopamp • 880MHz GBW; 40MHz FPBW @ 3Vpp into 100Ω; 1200V/µs • 2nV/√Hz @ 10kHz • ±5Vs max, 50mW @±5V (150mW if derived from ±15V) • 100 krads - needs shielding (300 kradreq) Dynamicrangeisreduced 3x by running@±5V ±10Vout requires ±15V supplies, not ±12V

  9. HF, MF Load Power • Need 100Ω loads for termination • Will cut amplitudes in half at receivers • 7Vrms^2/100 = 490mW • 2Vrms^2/100 = 40mW • Use AC coupled termination? • At what frequency? • What amplitude/power dissipation? • Frequency response will not be flat

  10. Some LF Choices • OP15/16 legacy op amp • 6-8MHz GBW; 15-25V/µs  • 10^12Ω Rin • 15nV/√Hz @ 1kHz  • 120/210mW@ ±15Vs  • 100 krads - needsshielding (300 kradreq) • OP27 • 8MHz GBW; 2.8V/µs  • 3x10^12 Rin • 3nV/√Hz @ 1kHz  • 100mW @±15Vs  • 100 krads - needs shielding (300 kradreq) • OPA602 • 6.5MHz GBW; 35V/µs  • 10^14 Rin • 12nV/√Hz @ 1kHz  • 90mW@±15Vs  • ??? krads – need to find out; used on Solar Orbiter

  11. Total Power(assuming termination load mitigation somehow) • Best case: • Run FETs, HF and MF @±5V • using AD8001, DC coupled term • Assume 100mW LF • LF = 100mW • MF = 50mW • HF = 50mW • Loads = 90mW • Total: • 290mW/preamp • X4.5 =1.26W • Worst case: • Run FETs, HF and MF @±15V • using AD844, AC coupledterm guess • Assume 150mW LF • LF = 150mW • MF = 225mW • HF = 225mW • Loads = 200mW • Total: • 800mW/preamp • X4.5 =3.4W

  12. Total Power • One possible compromise: • Run FETs@±15V and ÷2 into MF, HF stages, DC coupledterminations • Run MF and HF at ±5V derived from ±15V using AD8001 • Assume 100mW LF • LF = 100mW • MF = 150mW • HF = 150mW • Loads = 90mW • Total: • 590mW/preamp • X4.5 =2.46W • Price: • HF, MF dynamic range smaller • HF, MF noise RTI >>2nV/√Hz

  13. HF, MF Power Supply Rails SNR versus Vsupply: • ±5Vs • HF: 20MHz SNR(2Vrms/20nV/√Hz) = 85dB(300mVpp max Vin) • MF: 1MHz SNR(2Vrms/2nV/√Hz) = 118dB  (3Vpp max Vin) • ±15Vs • HF: 20MHz SNR (7Vrms/20nV/√Hz) = 96dB  (2Vpp max Vin) • MF: 1MHz SNR (7Vrms/2nV/√Hz) = 129dB  (20Vpp max Vin)

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