SIMTEC M-31 Bedienungsanleitung
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MODULAR AMPLIFIER
INSTRUCTION MANUAL
Serial Number
Simtec Ltd.
Cable: Simatom
3400 Metropolitan Blvd. East.
Tel. : (514) 728-4527.
Montreal 38, Quebec
Canada.
Printed in Canada
05661\1310
Warranty
Simtec equipment is warranted against defective
materials and workmanship for one year.
Queries regarding this warranty should be directed
to your Simtec Technical Representative.
The serial number and model of your unit should be
stated to your Simtec Representative when making enquiries.
Many faults may be dealt with in the field, with the benefit
of minimum down-time for your equipment.
Simtec reserves the right to adjust specifications
and prices without notice.
This publication copyright
0
1966 reserved by
Simtec Ltd., Montreal, Canada. No part may be reproduced
without permission of the copyright owner.
.25
.125
.063
4
8
12
FINE GAIN
COARSE GAIN x8
FIRST DIFFERENTIATOR
8
.65
.
.70
.60
:
75
4
1
.5
2
2
.25
16
1.0
•
1.125
.
.85
.063
.90
8 64
12
128
B.B.
256
.55.
.50
.
SECOND DIFFERENTIATOR
OUTPUT POLARITY
DIRECT
INVERTED
INTEGRATOR
1
.5
2
B.B.
BUFFER SECTION
UPPER CONTROL
LOWER CONTROL
IN IN
OUT
IN
OUT
IN
A.C.OUT
)10
93ohms
93ohms
93ohms
NORMAL
NORMAL
NORMAL
4
44)
TERM. OFF
NO CONN.
NO CONN. D.C.
OUT (i.)
MODULAR AMPLIFIER M-31
4
32
Figure 1. SIMTEC M-31 MODULAR MAIN AMPLIFIER
Type M-31 Modular Main Amplifier is shown on the
opposite page with its controls and switches in a standard
position. With the toggle switches (Si to S4) in the normal
upward position, the preamplifier signal is introduced at the
first BNC connector on the left (J1) and, after amplifying
and shaping within the amplifier, is taken out at the extreme
right either by
a.c. coupling
(the upper connector J7) or by
direct coupling, (the lower connector J8).
The input termination switches (Si and S2) are shown
in the upward or terminated position suitable for most pre-
amplifiers. When in downward position each gives 1000 ohms
input impedance.
Controls in the Upper Control section are shown
with Fine Gain at 1.0, the maximum; the Coarse Gain knob
(outer) is shown at
8x
and the First Differentiator at 1 micro-
second.
In the Lower Control section, the Output Polarity is
set to Direct, giving the same pulse polarity at both input and
output of the M-31; the Integrator control is set to 1 micro-
second and the
Second
Differentiator is set to Broad-Band, thus
giving a monopolar pulse.
When
the controls are set as above,
the noise relative to the input is less than 15 microvolts.
(For detailed explanation of the control functions,
please refer to the text.)
CHARACTERISTICS
General
The Simtec M-31 Modular Main Amplifier is a high gain audio
to radio frequency amplifier for use in shaping and amplifying
pulses from nuclear radiation detectors. Its power is drawn
normally from an AEC Standard Bin, but may be taken from many
supplies of similar specification. Pulse Shaping and amplifica-
tion are accomplished by resistor-capacitor net-works in con-
junction with high speed operational amplifiers. Successive
shaping and gain operations are performed on the pulses as they
pass through the amplifier. The sequence and nature of these
operations is chosen to optimize the signal to noise ratio and
saturation characteristics of the amplified pulses, for all
input pulse rates and signal magnitudes.
Operational Amplifiers
The individual plug-in high speed operational amplifiers
have gain-bandwidths in excess of 1500 MHz and may give closed
loop risetimes as fast as 20 volts in 35 nanoseconds; these
capabilities are relaxed in each of the six operational amplifier
positions in the interest of overall stability. The operational
amplifiers all have differential inputs, a feature which gives
high common-mode rejection for power supply disturbances and
other forms of interference. The operational amplifiers are
direct-coupled internally, a feature which gives optimum
recovery from overload and which, together with the differential
inputs, provides maximum gain stability through stabilization of
the transistor bias points.
Feedback Control
Feedback networks are used for pulse shaping and gain
determination rather than interstage attenuating networks for
the following reasons:
---Potentiometer loading effects are eliminated; thus gain and
time determining circuit elements may be given values which
are simple ratios to one another.
---Resistor-capacitor combinations may be used exclusively
in networks which synthesize transients. Capacitors have
the advantage over inductances that for wide frequency ranges
they have better phase shift and dissipation characteristics;
moreover, the quality of component required for the level of
stability achieved in the M-31 is more readily available in
capacitors than in equivalent inductances.
---Signal to noise ratio is nearly independent of gain; at
minimum gain, signal to noise ratio of the amplifier with
gain control in the feedback loop is much superior to that
for the amplifier with interstage attenuators, because with
the former the noise of the gain stage is reduced in propor-
tion to the signal, but not with the latter.
---Gain stability is not favored by amplifiers with interstage
attenuators and filters; loading effects on interstage net-
works demand that these networks see constant impedances at
both input and output. When gain and shaping are determined
by feedback networks, these computing networks are not loaded
by the surrounding circuitry and no instability can result
from this source.
Front Panel Arrangement
Each section of the M-31 is provided with controls and/or
connections on the front panel of the AEC standard four-width
module. In the schematic diagram, BNC connectors are numbered
from left to right on the front panel, as are the switches.
Connections marked "Buffer Section" are associated with Opera-
tional Amplifier No. One. Connections marked "Upper Control"
are associated with Operational Amplifiers Two and Three; this
group is controlled by the "First Differentiator "and" Coarse
Gain" rotary switch, and by the "Fine Gain" potentiometer
to its left. Connections marked "Lower Control" are associated
with Operational Amplifiers Four, Five and Six; this group is
controlled by the "Integrator" and "Second Differentiator"
switch and by the "Polarity" switch to its left.
Power Requirements
The M-31 requires about
8.4
watts of D.C. power as follows:
24 volts at 150 ma and ± 12 volts at 50 ma. This power is
available from any modular power supply of The NBS/AEC standard
type (per TID 20893, Louis Costrell) or of The Lawrence
Radiation Lab.
Linear Amplifier 11x198 type of bin supply
(Goulding and Landis design,
used by
several
manufacturers).
Ripple and regulation specifications
of either
of these types
of supplies are adequate for
most high
quality spectroscopy.
Power decoupling and gain stabilization within the M-31 permits
use with a wide variety of supplies.
When used without an AEC Standard Bin, The noise suppression
and shielding precautions within the M-31 are adequate for most
use on the bench, or in a nonstandard rack mount.
Power Connections
The mating connector required is an AMP No. 202516-3, 42
pin female block, with AMP "Type III
" Socket contacts mounted
as follows:
Pin number 16 12 volts
17 - 12 volts
28 4- 24 volts
29 - 24 volts
34 - GROUND.
Shielding of the nonstandard cable may or may not be required,
depending on the severity of the RFI environment.
Grounding
For optimum system noise performance, a certain minimum
of care must be taken with the grounding. Precautions advised
are:
1
Make sure that grounds for the preamplifier, detector
bias supply and M-31 are
close
to being the same ground,
when the single input is used; and
2
when ground at the preamplifier is "exported" through
a cable for common mode rejection of pickup, try to match
the cable lengths and source impedances as exactly as
possible for minimum readjustment of RVI and
c3
common
mode trimmers.
Construction Features
The M-31 fits four module widths (5.4 inches) of a standard
AEC bin. It consists of ten major assemblies as noted on the
system schematic. Six of
these
assemblies are the six opera-
tional amplifiers which are plug-in units mounted in individual
shield cans over 22-pin edge connectors. The edge connectors,
in turn are mounted on a common assembly called the "mother
board" which contains the bulk of passive components not mounted
on the Upper or Lower Control rotary
switches.
Each operational amplifier
has
a small hole near the top
end which permits removal for servicing or inspection.
Each transistor is socket mounted, also for ease of inspection
or replacement should the need arise.
Each of the three major outputs has a spare high stability
resistor mounted on the mother board as indicated on the system
schematic. This feature permits the user to mount extra
connections on front or back panel of the module at a later time
should the need arise. The common source impedance directly on
the output of each operational amplifier is less than 0.1 Ohm
when two or more such loads are used.
All semiconductors used in the M-31 are silicon units, unselected.
All precision resistors surpass specification MIL-R-10509E,
Characteristic "C" or better in all gain-determining positions.
All carbon resistors are of the high-stability, high reliability,
hot molded type, surpassing performance required by specification
MIL-R-IIE, Characteristic "G".
The etched wiring boards are of high peel strength double-sided
glass epoxy laminate.
