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SiPM Amplifier Optimization (view source)
Revision as of 20:51, 4 February 2009
, 20:51, 4 February 2009no edit summary
[[Image:AmpVis_v6_DC.png|frame|center|DC characteristics of the amplifier. Units of V, mA, and Ω are implied unless corrected by different prefix.]]
[[Image:AmpVis_v6_DC.png|frame|center|DC characteristics of the amplifier. Units of V, mA, and Ω are implied unless corrected by different prefix.]]
==== The gain switch ====
==== The Gain Switch ====
A MOSFET switch the effective collector resistor in the first stage of the summing circuit between about 3 kΩ due to R<sub>e</sub> alone and the parallel path of 165 Ω. NXP's BF1108R has been selected for prototyping. Its typical <math>V_{GS}</math> for current pinch-off is -3 V (max: -4 V). Putting its source on the supply rail and switching the gate between 5 V (on) and 0 V (off). A bypass capacitor (not shown in diagram) near the gate lead is important to prevent spurious switching.
A MOSFET switch the effective collector resistor in the first stage of the summing circuit between about 3 kΩ due to R<sub>e</sub> alone and the parallel path of 165 Ω. NXP's BF1108R has been selected for prototyping. Its typical <math>V_{GS}</math> for current pinch-off is -3 V (max: -4 V). Putting its source on the supply rail and switching the gate between 5 V (on) and 0 V (off). A bypass capacitor (not shown in diagram) near the gate lead is important to prevent spurious switching.