SPP FIELDS Preamplifier Peer Review 24OCT2013

SPP FIELDS Instruments Digital FIELDS Board (DFB) DC to 64kHz (LF) 20nV/√Hz noise floor, 120Vpp max signals Time Domain Sampler (TDS) 3kHz to 1MHz (MF) 20nV/√Hz noise floor, 20Vpp max signals Radio Frequency Spectrometer (RFS) 30kHz to 20MHz (HF) 3-4nV/√Hz noise floor, 4Vpp max signals

SPP FIELDS Preamplifier

SPP FIELDS Preamplifier Concept - V1-V4

SPP FIELDS Preamplifier Concept – V5

SPP FIELDS Preamplifier Requirements Input RTI = antenna whip connector on preamp Input impedance > 1E+9 Ohms Input current < 2E-8 Amps Input capacitance < 40pF LF output Noise RTI < 1uV/√Hz above 100Hz Max input amplitude WRT FGND 20Vpp +/-20V -3dB bandwidth > 64kHz Gain 1 +/-0.01%, DC to 300Hz 1 +/- 0.1%, above 300Hz Output resistance 249 Ohms +/-0.1%, 100ppm/C

SPP FIELDS Preamplifier Requirements MF output Noise RTI < 30nV/√Hz above 1kHz Max input amplitude WRT FGND 20Vpp +/-20V -3dB bandwidth > 200kHz Small signal -3dB bandwidth > 1MHz Gain 1 +/- 1% Output resistance 249 Ohms +/-5% HF output Noise RTI < 10nV above 100kHz; <4nV above 1MHz 4Vpp output -3dB bandwidth > 20MHz Gain 2 < gain < 10 Output resistance 50 Ohms +/-5%

SPP FIELDS Preamplifier Environmental Radiation: 70krad total dose inside 0.1” aluminum box All parts are SQPL 100krad or better except JFET LSK389   Thermal: 0.25AU to 9.5Rs min surv w/ htr max surv min ops max ops V1-V4 -125 -65 @ ?W 75 -40 V5 -220 -65 @0.75W 60 -180 5

BACKUP SLIDES

Original Design

Testing

Input Capacitance Test Measured 20pF and test box strays with meter Measured HF gain at low and high frequencies C in = (20pF/Hfgain)-20pF Conclusions: Find alternative clamp diodes (DPAD or 2N5547) Consider eliminating? Evaluate risk U404, 2N5547 Cin not much lower, have 40-60% higher noise and inadequate gain bandwidth LSK389 HF gain = 20/(60+25+20) = 0.19 Galaxy will = 10% increase in 3nV amp noise above 1MHz 60pF C base mitigates effect of JFET C in Results: LSK389 = 50pF with LSK389 as clamp diodes (not shown) LSK389 = 25pF without clamp diodes U404 and 2N5547 = 12-15pF

Noise Test Setup

HF Noise, Original Design

LF Noise, Original Design

Signal Evaluation Test Setup - Original Design

Signal Evaluation Test Setup - Proposed Design

MF Frequency Response Vs. Simulations

MF Harmonics - Original Design

MF Harmonics - Proposed Design

MF Harmonics - Proposed Design, Improved

Preamp Design To Do List Evaluate tradeoffs in changes to mitigate harmonics Do complete transfer function measurements with amplitude and phase Measure thermal drifts from -80 to +80 Choose overall values for high and low gains

SPP FIELDS Preamplifier: LF Bootstrap

SPP FIELDS Preamplifier: LF Biasing

SPP FIELDS Preamplifier: HF antenna coupling

SPP FIELDS Preamplifier - Signal Levels 0.25 AU (54 Rs): R plasma ~ 1MΩ C coupling = 20pF Gain = 0.25 @ >10kHz

SPP FIELDS Preamplifier - Signal Levels R plasma ~ 10kΩ C coupling = 20pF Gain = 0.25 @ >1MHz

SPP FIELDS Preamplifier - HF Signals Assuming 20pF source capacitance 60pF input capacitance

SPP FIELDS Preamplifier Requirements LF requirements Comments [a] Input impedance > 1E+11 Ohms; 100GΩ; PA can meet this, but it is inappropriate for SPP environment and should be changed to reflect AEB loop gain requirements and expected plasma impedances [b] Input current < 2E-8 Amps; 20nA;Easily met; OP15 max = 110pA across temperature, LSK389 is 0.1pA @25C [c] Input capacitance < 5 pF; Should be revised; was originally written for OP15 alone but FET and strays are 25pF; can change to 40pF but real limit requires antenna characterization [d] Noise @ 100 Hz < 1000 nV/√Hz; From science requirements; OP15 is 20nV [e] -3 dB frequency ~ 500 Hz; Should be deleted; this is actually the AEB FGND driver spec [f] -3dB small signal BW > 64 KHz; Guaranteed by OP15 GBW and SR [g] Max Input amplitude > 20 Vpp; Should be revised to max =20Vpp WRT FGND [h] Gain of 1; Should probably state accuracy of 0.1%; not to be confused with AEB loop gain accuracy [i] Output resistance < 100 Ohms. Should be revised based on AEB LF loop DC gain requirements and should include accuracy and tempco

SPP FIELDS Preamplifier Requirements MF requirements Comments [a] Input impedance > 1E+9 Ohms; Redundant; delete or separate into input and output requirements [b] Input current < 2E-8 Amps; [c] Input capacitance < 10 pF; [d] Noise @ 100kHz < 20 nV/√Hz; OP15 = 15nV @ 1kHz [e] -3 dB frequency > 3 KHz; This is roll-on frequency and has not been decided; delete? [f] -3dB small signal BW > 1MHz; Guaranteed by OP15 GBW and SR [g] Max Input amplitude > 6 Vpp; Should be revised to reflect change to shared output from OP15 for LF+MF [h] Gain of 1; Should probably state accuracy [i] Output resistance < 240 Ohms. Revise to = 249 Ohms +/-5% or delete

SPP FIELDS Preamplifier Requirements HF requirements Comments [a] Input impedance > 1E+9 Ohms; Redundant; delete or separate into input and output requirements [b] Input current < 2E-8 Amps; [c] Input capacitance < 10 pF; [d] Noise @ 100 KHz < 4 nV/√Hz; Revise to <10nV @ 100kHz and <4nV @ 1MHz and state that this is referred to FET gate [e] -3 dB frequency > 30KHz; This is roll-on frequency; state differently? [f] -3dB small signal BW > 20 MHz; Easily met with AD8001 [g] Max Input amplitude > 0.9 Vpp; State that this is referred to FET gate [h] Gain of 7; To be revised depending on antenna characteristics; set min/max? delete? [i] Output resistance < 50 Ohms. Revise to "50 Ohms +/-5%"