Status Report

Status Report2010.7.9Atsushi Nukariya

Circuit of FET charge amplifier

Setting base voltage of . Cutting AC. This capacitor stabilizes voltage which sets. (Bypass capacitor)Explanation of Circuit

Emitter follower. Amplification of current. Decreasing effects of previous circuit. Amplification of voltage doesnt occur. Folded cascode connection. Amplification of voltage. Source of noise is here.Explanation of Circuit

Offset voltage and dynamic rangeOffset voltage (DC of ) affects on dynamic range.

Offset voltage and dynamic rangeVoffset = 0Voffset = -aDynamic range of plus sideGND Input of pulser Output of pre-ampDynamic range of minus sidea If offset voltage is plus, dynamic range of plus side becomes small and that of minus side becomes big. If offset voltage is minus, dynamic range of minus side becomes small and that of plus side becomes big.

Input pulse Pulser : Agilent 81110A Delay : 0 [ps] Width : 100.0 [s] LeadE : 100 [ns] TraiE : 50.0 [ns] High : +0.0 [mV] Low : variable 50 [] into 50.0 []WidthLowHigh

Offset voltage Input of pulser Output of pre-amp Output of probeGND(51 resistance forward)Offset voltageOffset voltage is -240 mV. Dynamic range of minus side will be smaller than that of plus side.

Dynamic range Input of pulser Output of pre-ampVin = 140 [mV]Vin = 660 [mV]Vin = 1650 [mV]Dynamic range of minus side is -100mV.Dynamic range of plus side is 1420mV or more.

Dynamic rangeVin = 660 [mV]Vin = 1650 [mV] Input of pulser Output of pre-ampIncreasing time that output voltage of pre-amp is -100mV. Amplification of minus side becomes large. Time that output of pre-amp is minus after amplification of plus side becomes long.

Problem in dynamic range Dynamic range of plus side is unknown. 1420mV is the limit voltage that dynamic range of plus side can be obtained correctly when input pulses width is 100.0s. Using the saw pulse instead of the rectangular pulse. Dynamic range of minus side is smaller than Kato-sans expectation value. I dont understand Kato-sans idea completely. Obtaining dynamic range of plus side and calculating of dynamic range are next plan. I wonder this result is caused for the frequency response.

GainGain formula is (output voltage of pre-amp) / (input voltage) . Gain of plus side is below 1. Gain of minus side cant be obtained because of exceeding from dynamic range. Kato-san said that this result is correct. Because if this result is correct I cant explain the effect of amplification of voltage at folded cascode connection, I cant understand this result.Input voltageOutput voltage Amplification of plus side Amplification of minus side

Graph1

6060

110110

100160

100220

100280

100330

100380

100440

100480

100540

100600

100650

100720

100780

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100930

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0

706060

140110110

200100160

260100220

330100280

400100330

460100380

530100440

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660100540

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860100720

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16501001420

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Next plan Clarification of the relation between offset voltage and dynamic range. Change of shape of input pulse. Understand of the role of folded cascode connection about gain.