Low noise charge sensitive preamplifier DC stabilized without a physical resistor

Patent · Tue Sep 13 04:00:00 EDT 1994

OSTI ID:869497

Bertuccio, Giuseppe ^[1]; Rehak, Pavel ^[2]; Xi, Deming ^[3]

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1. Brianza, IT
2. Patchogue, NY
3. Beijing, CN

The invention is a novel charge sensitive preamplifier (CSP) which has no resistor in parallel with the feedback capacitor. No resetting circuit is required to discharge the feedback capacitor. The DC stabilization of the preamplifier is obtained by means of a second feedback loop between the preamplifier output and the common base transistor of the input cascode. The input transistor of the preamplifier is a Junction Field Transistor (JFET) with the gate-source junction forward biased. The detector leakage current flows into this junction. This invention is concerned with a new circuit configuration for a charge sensitive preamplifier and a novel use of the input Field Effect Transistor of the CSP itself. In particular this invention, in addition to eliminating the feedback resistor, eliminates the need for external devices between the detector and the preamplifier, and it eliminates the need for external circuitry to sense the output voltage and reset the CSP. Furthermore, the noise level of the novel CSP is very low, comparable with the performance achieved with other solutions. Experimental tests prove that this configuration for the charge sensitive preamplifier permits an excellent noise performance at temperatures including room temperature. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using a commercial JFET as input device of the preamplifier.

• Research Organization: ASSOC UNIVERSITIES INC
• DOE Contract Number: AC02-76CH00016
• Assignee: Associated Universities, Inc. (Washington, DC)
• Patent Number(s): US 5347231
• Application Number: 08/021,239
• OSTI ID: 869497
• Country of Publication: United States
• Language: English

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