ORTEC 109A PREAMPLIFIER

DESCRIPTION
The 109A is an all-transistor preamplifier with pole-zero cancellation using a field-effect transistor in the input stage. The circuitry includes a charge-sensitive input loop, an Amplifier stage with switch selectable gain with a 10:1 ratio, and a cable driver stage.  The preamplifier is inherently an inverting preamplifier; i.e., a negative input pulse yields a positive output pulse. No pulse shaping is accomplished in the preamplifier, except for a pole-zero-cancelled 50 uSec differentiation time constant immediately after the charge-sensitive loop, for the purpose of reduction of pulse pileup at high count rate.  System pulse shaping for optimization of signal-to-noise ratio will be accomplished in the subsequent main amplifier.

SPECIFICATIONS
Basis of Warranty
<=0.025 keV/pF FWHM (Ge) slope, 2.5keV FWHM (Ge) maximum at 0pF input capacity.  Typical performance is given below:

TYPICAL PERFORMANCE 

Input Capacitance (pF)	Noise with 2 uSec Single RC Main Amp			Preamplifier Output Pulse
	FWHM Si (keV)	FWHM Ge (keV)	No. of rms Electrons	Relative Amplitude	Rise Time (nSec), 10 - 90%
0	2.85	2.29	336	1.000	15
20	3.2	2.6	377	1.000	19
50	3.72	2.99	440	1.000	25
100	5.1	4.1	601	0.996	40
200	7.9	6.4	931	0.993	68
500	16.2	13.0	1910	0.982	175
1000	30.4	24.4	3580	0.963	250

 
 

Output Pulse Shape	Rise time as in table above, exponential fall with 50 pSec time constant
Integral Nonlinearity	<=0.1% for 0-5V output span with internal series termination
Temperature Coefficient	+/-0.01%/'C
Detector Bias Isolation	1000V dc
Input Open Loop Gain	> 20,000
Power Required	+24V dc at 36mA, -24V dc at 36mA  Supplied from ORTEC main amplifier or from an ORTEC 114 or 115 Preamplifier Power Supply
Power Cable	10-ft captive power cable is furnished with each 109A
Power Connector	Amphenol 17-20090
Saturated Output Amplitude	7 V at end of several hundred feet of unterminated 93 Ohm cable
Output Source Impedance	Adjustable from 50 to 150 Ohm
Charge Sensitivity	150mV/MeV (Si), 183mV/MeV (Ge) in X10 gain position; 15mV/MeV (Si), 18.3 mV/MeV (Ge) in X1 gain position
DETECTOR, OUTPUT   AND TEST Pulse Connectors	BNC
DETECTOR BIAS Connector	SHV
Size	Size 1.8 x 4 x 6 inches (4.5 x 10.2 x 15.3 cm)
Weight	Weight Net, 1.5 lb (0.7 kg); gross 2.3 lb (1.1 kg)

 

COUNT RATE VS. ENERGY
See data below, from which it is obvious that in almost all cases, the count rate is limited by the shaping amplifier.
 

Input Energy (MeV)  (Si Equivalent)	Count Rate with 1%  Counting Losses (cts/sec)
0.1	2*109
1	2*107
10	2*105