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 Dynamic Range ±10V at LF in, x1 Gain ±10V at MF in, x1 Gain ±1V at HF in, x10 Gain

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

AD mW AD mW OPA602 90mW 44mW 490mW >1 W!! FETs 60mW Termination power Probably unrealistic – but what is realistic?

AD mW AD mW OPA602 90mW 44mW 490mW W AC coupled terminations, ignored Non-flat response Freq? Ampl? FETs 60mW

AD mW OPA602 90mW 44mW 490mW 0.45 W AC coupled terminations, ignored MF  ±5V FETs 60mW

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

HF, MF Power Some typical op amp choices AD844 current feedback op amp – 60MHz GBW; 20MHz 20Vpp into 100Ω; 1200V/µs – 1kHz – ±15Vs; – 100 krads - needs shielding (300 krad req) AD8001 current feedback op amp – 880MHz GBW; 40MHz 3Vpp into 100Ω; 1200V/µs – 10kHz – ±5Vs max, (150mW if derived from ±15V) – 100 krads - needs shielding (300 krad req) Dynamic range is reduced 3x by ±10Vout requires ±15V supplies, not ±12V

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

Some LF Choices OP15/16 legacy op amp – 6-8MHz GBW; 15-25V/µs – 10^12Ω Rin  – 1kHz  – ±15Vs  – 100 krads - needs shielding (300 krad req) OP27 – 8MHz GBW; 2.8V/µs  – 3x10^12 Rin – 1kHz – – 100 krads - needs shielding (300 krad req) OPA602 – 6.5MHz GBW; 35V/µs – 10^14 Rin – 1kHz  – – ??? krads – need to find out; used on Solar Orbiter

Total Power (assuming termination load mitigation somehow) Best case: Run FETs, HF and 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 using AD844, AC coupled term guess Assume 150mW LF LF = 150mW MF = 225mW HF = 225mW Loads = 200mW Total: 800mW/preamp X4.5 = 3.4W

Total Power One possible compromise: Run and ÷2 into MF, HF stages, DC coupled terminations 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

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 )