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Status Report

Status Report. 2010.7.9 Atsushi Nukariya. Circuit of FET charge amplifier. Explanation of Circuit. ・ ○ ・・・ Setting base voltage of ○ . ・ ○ ・・・ Cutting AC. → This capacitor stabilizes voltage which ○ sets. (Bypass capacitor). Explanation of Circuit. ・ ○ ・・・ Emitter follower.

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Status Report

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  1. Status Report 2010.7.9 Atsushi Nukariya

  2. Circuit of FET charge amplifier

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

  4. Explanation of Circuit ・○ ・・・ Emitter follower. → Amplification of current. Decreasing effects of previous circuit. Amplification of voltage doesn’t occur. ・○ ・・・ Folded cascode connection. → Amplification of voltage. Source of noise is here.

  5. Offset voltage and dynamic range ・Offset voltage (DC of ●) affects on dynamic range.

  6. Offset voltage and dynamic range Voffset = 0 Voffset = -a Dynamic range of plus side a GND Dynamic range of minus side ーInput of pulser ーOutput of pre-amp ・ 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.

  7. Input pulse ・ Pulser : Agilent 81110A ・ Delay : 0 [ps] ？ ・ Width : 100.0 [μs] ・ LeadE : 100 [ns]？ ・ TraiE : 50.0 [ns]？ ・ High : +0.0 [mV] ・ Low : variable ・ 50 [Ω] into 50.0 [Ω] Width High Low

  8. Offset voltage GND ●(51Ω resistance forward) Offset voltage ーInput of pulser ーOutput of pre-amp ーOutput of probe ・Offset voltage is -240 mV. 　→ Dynamic range of minus side will be smaller than that of plus side.

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

  10. Dynamic range Vin = 660 [mV] Vin = 1650 [mV] ーInput of pulser ーOutput of pre-amp ・Increasing 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.

  11. 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 pulse’s width is 100.0μs. 　→ Using the saw pulse instead of the rectangular pulse. ・ Dynamic range of minus side is smaller than Kato-san’s expectation value. 　→ I don’t understand Kato-san’s 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.

  12. Gain ▲ Amplification of plus side ▲ Amplification of minus side Output voltage Input voltage ・Gain formula is (output voltage of pre-amp) / (input voltage) . 　→ Gain of plus side is below 1. Gain of minus side can’t be obtained because of exceeding from dynamic range. 　→ Kato-san said that this result is correct. Because if this result is correct I can’t explain the effect of amplification of voltage at folded cascode connection, I can’t understand this result.

  13. 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.

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