EG&G ORTEC 474 Manual de operação e serviço - Página 9

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Table 6.1. Typical dc Voltages
NONINV mode; Diff and Int switches set to "Out"; Fine Gain
2; Coarse Gain = 1.
Q1B
-2.7 mV
018E
-29 mV
Q1E
-0.6 V
019B
8.65 V
QIC
12.0 V
0190
11.70 V
Q2B
45 mV
O20B
-8.65 V
020
5.90 V
O20O
-11.70 V
03E
5.35 V
101(2)
-2.6 mV
Q4B
-6.76 V
101(3)
-2.2 mV
Q4E
-7.40 V
101(4)
-12 V
Q5B
-7.40 V
101(6)
-70 mV
Q6E
-7.30 V
101(7)
12 V
07B
14.50 V
A1(1)
100 mV
Q7E
13.95 V
A1(2)
120 mV
Q8E
14.55 V
A1(3)
-0.50 V
Q9B
90 mV
A1(4)
17 mV
Q9E
0.73 V
A1(5)
0 mV
090
-9.25 V
A1(6)
-11.5 V
O10B
7.60 V
A1(7)
-5.8 V
O10E
8.25 V
A1(8)
0 V
011B
8.20 V
A1(9)
0.65 V
0110
12.0 V
A1(lb)
11.7V
012E
8.20 V
A2(1)
-17 mV
0120
1.27 V
A2(2)
-1.0 mV
013E
1.21 V
A2(3)
-0.6 V
0130
-1.25 V
A2(4)
40 mV
014E
-9.85 V
A2(5)
-56 mV
0140
-1.31 V
A2(6)
-11.5 V
015E
0.66 V
A2(7)
-5.8 V
0150
8.0 V
A2(8)
0 V
016E
25 mV
A2(9)
0.77 V
017E
-0.68 V
A2(10)
11.7 V
0170
-8.0 V
7.
APPLICATION NOTES
7.1.
GENERAL
The most important function that is served by the 474
Timing Filter Amplifier is pulse shaping. This is especially
important when using the output from a large volume de
tector, with a wide range of charge-collection times for
its output pulses, and attempting to obtain timing infor
mation from these nonuniform pulses. By adjusting the
pulse risetime with the 474 to an interval that is longer
than any of the input risetimes, the 474 output pulses will
have the advantage of uniformity. The pulse decay time
constant is also selectable so that the operator can com
promise between pulse-pair resolution time and system
noise; as shorter time constants are used, pulse-pair
resolution time is shortened at the expense of an increase
in noise.
Other functions that are also included in the 474 are linear
amplification of small pulses of either polarity, polarity
control, and adjustable pole-zero cancellation. These
additional features provide useful functions in most of
the circuits where pulse shaping is necessary.
Each application for the 474 will require a different com
bination of the data enhancement parameters that are
available. Use each as required in the specific application.
7.2.
CONSTANT-FRACTION TIMING
WITH GERMANIUM DETECTORS
Figure 7.1 is a block diagram of a gamma-gamma coin
cidence sy.stem that can be used for timing with germa
nium detectors. In this system the TPHC start channel