The CHARGE8V Charge Sensitive Preamplifier

The CHARGE8V is a general purpose charge integrating preamplifier (JFET input RC charge reset type with
bipolar output) suitable for use in a wide range of applications.  Some uses include:

Solid state radiation detectors  - (including position sensitive) such as Si surface barrier, PIN photo diode, Si
strip, GeLi, CdZnTe, etc.

Gas filled radiation detectors - (including position sensitive) such as Ion chambers, proportional counters,
Time projection chambers, Bragg curve detectors, low pressure proportional counters, MWPC, PPAC, etc.

Scintillation radiation detectors - Photo multiplier, and PIN photo diode readout.

Instrument applications - readout of dynode and microchannel electron multipliers, channeltrons, or other
applications when the output is a charge pulse and low noise is necessary.


Sensitivities - of 160 mV/MeV Si (3.6 mV/fc) to very low values are possible.

Output impedance - 50 Ohm

Output range - greater than +-8 V into 1k Ohm,  greater than +-3 V into 50 Ohm

Rise time -  with sensitivity set at 160 mV/MeV Si,  Rt ~15 ns with 0 pf In. C, ~60 ns with 100 pf In. C.
                     with sensitivity set at 5 mV/MeV Si,  Rt  ~10 ns with 0 pf In. C, ~30 ns with 100 pf In. C.

Power dissipation - ~300 mW,  ~ 15 mA @ +12 Volt,  ~10 mA @ -12 Volt

Note the noise width in the Am241 X-ray spectrum above.  This is with the preamp risetime set at 10 ns and the input J-FET protection diode removed using the circuit below labled "DC Coupling Application".  This shows that the pre-amp noise is lower at 10 pf than the pulser data indicates in the graph above.  The FWHM value is worst case (FWHM + Error).

Remote FET Application

DC Coupling Application

Note:  The best power supply voltage and polarity protection is achieved using transient voltage supression shunt
diodes with a polyswitch resetting type fuse.  This results in the lowest possible voltage drop.  Common mode noise filters should be placed upstream if they are necessary.