Temperature dependent characteristics of the 2N4416 JFET for radiation spectrometer charge-sensitive pre-amplifiers

Feedback resistor-less charge-sensitive pre-amplifiers for X-ray/γ-ray photon (and e^- particle) counting photodiode radiation spectrometers operate with their input transistor in an unusual mode (i.e. the gate is slightly forward biased). This enables better (lower) noise performance than is possible with traditional charge-sensitive pre-amplifiers. Optimal pre-amplifier operation requires careful setting of the biasing condition of the transistor, which requires knowledge of its operating characteristics. However, transistor manufactures do not commonly include the necessary details on their data sheets, as this is an atypical application. Here, the characteristics of the popular 2N4416 junction field effect transistor operated in this mode are reported for the first time across the temperature range -70 °C ≤ T ≤ 100 °C, and the optimal biasing conditions for the illustrative situations of no, low (pA), and moderate (nA) detector leakage currents are reported.