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SPP FIELDS Preamp Power Requirements

SPP FIELDS Preamp Power Requirements. 01DEC2012 D. Seitz. 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.

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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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