“Gate-to-gate” BJT obtained from the double-gate input JFET to reset charge preamplifiers

A novel charge restoration mechanism to reset charge sensitive preamplifiers is presented. The “gate-to-gate” Bipolar Junction Transistor transversal to the input JFET with independent top and bottom gates is exploited as a “reset transistor” embodied in the preamplifier input device. The p—n junction between the bottom gate and the channel is forward-biased by a proper feedback loop supplying the necessary restoration current to the input node capacitance through the top gate-channel reversed-biased junction. The continuous reset mode is here analysed with reference to the DC stability, the pulse response and the noise behaviour. Experimental results are reported.