Charge preamplifier

Claim 2

A charge preamplifier essentially comprising an input stage driven by the signal to be amplified, said stage being connected to an amplification stage which is in turn associated with an output stage, and a circuit for applying feedback from the output to the input of said preamplifier, said feedback being of the optoelectronic type, said input stage being such as to comprise a field-effect transistor cooled below ambient temperature, the signal to be amplified being applied to the input gate of said transistor, the load resistance of said transistor being provided by a second field-effect transistor mounted in series with an inductance coil.

Claim 3

A preamplifier according to claim 1, wherein the impedance of said inductance coil within the frequency range of the preamplifier is considerably higher than the reciprocal of the slope of the field-effect load transistor.

Claim 4

A preamplifier according to claim 1, wherein the drain output of the input transistor is connected on the one hand to the source input of the load transistor through said inductance coil which is mounted in series with a resistor and on the other hand to the input gate of said load transistor.

Claim 5

A charge preamplifier essentially comprising an input stage driven by the signal to be amplified, an amplification stage conncted to said input stage, an output stage associated with said amplification stage, and a circuit for applying feedback from the output to the input of said preamplifier, said feedback being of the optoelectronic type, said input stage comprising a first field-effect transistor cooled below ambient temperature, the signal to be amplified being applied to the input gate of said first field-effect transistor, a second field-effect transistor connected in series with an inductance coil as the load resistance of said first field-effect transistor, said feedback circuit comprising a comparator having one input connected to the output of said output stage and the other input connected to a reference voltage source, the output of said comparator being connected to means for initiating the supply of an electroluminescent diode placed opposite to the input of said first field-effect transistor, and a capacitor having one plate connected to the output of said output stage and the other plate connected to the input gate of said first field-effect transistor.

Claim 6

A charge preamplifier essentially comprising an input stage driven by the signal to be amplified, an amplification stage conncted to said input stage, an output stage associated with said amplification stage, and a circuit for applying feedback from the output to the input of said preamplifier, said feedback being of the optoelectronic type, said input stage comprising a first field-effect transistor cooled below ambient temperature, the signal to be amplified being applied to the input gate of said first field-effect transistor, a second field-effect transistor connected in series with an inductance coil as the load resistance of said first field-effect transistor, said feedback circuit comprising a comparator having one input connected to the output of said output stage and the other input connected to a reference voltage source, the output of said comparator being connected to means for initiating the supply of an electroluminescent diode placed opposite to the input of said first field-effect transistor, and a capacitor having one plate connected to the output of said output stage and the other plate connected to the input gate of said first field-effect transistor.

Claim 7

A preamplifier according to claim 4, wherein the feedback circuit comprises a delay circuit at the output of the comparator, a bistable circuit controlled by the logical state of the output of the comparator, said circuit being capable of supplying a bipolar transistor whose collector is connected to the input of the electroluminescent diode.