Feedback-controlled pulse-amplitude integrator and amplifier is used as an analog-to-digital converter that converts event-liberated charges, emanating from a nuclear-particle detector, directly to numbers rather than to analog-dependent voltages

Goldsworthy, W. W.

English

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November 1969	 Brief 69-10640 
AEC-NASA TECH BRIEF 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Pulse-Height Analyzer with Digital Readout 
The problem: 
To devise an electronic circuit for measurement 
of the amplitude of electric pulses from nuclear-
radiation detectors. Conventionally a pulse is passed 
through linear amplifiers and applied to a pulse-
height detector, and the result is converted to digital 
form for storage. 
The solution: 
A feedback-controlled pulse-amplitude integrator 
and amplifier used as an analog-to-digital converter
that converts event-liberated charges, emanating 
from a nuclear-particle detector, directly to numbers 
rather than to analog-dependent voltages. 
In this circuit a pulse is amplified in an amplifier 
that need not be linear, and the amplitude is immedi-
ately read in digital form. The amplifier is arranged as 
an integrating circuit. When an input pulse is received 
and integrated, a series of discrete feedback signals 
are applied to the amplifier input to return the input 
potential to zero. The required number of such feed-
(continued overleaf) Aft
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back signals is counted and read out as a digital indi-
cation of pulse amplitude. This technique simplifies 
the circuit overall, improves overload performance, 
and lessens dependence on amplifier-circuit stability. 
How it's done: 
For direct analog-to-numerical conversion, an am-
plifier (see figure), employing an integrating first stage, 
is employed as a null amplifier to control the flow rate 
of input-recharge pulses necessary to reestablish an 
original input balance. The number of these recharge 
impulses needed is summed in an address scaler and 
later transferred into a memory as a number. 
Nuclear-event-induced input charges collected at the 
output of a detector are converted to numbers by 
metering of the amount of charge necessary for com-
plete restoration of the input charge to its original 
state. This requires only a null-seeking system with 
metered restitution. 
An input-integrator circuit provides an output volt-
age proportional to the differential accumulated 
charge, and a moderate-gain direct-coupled amplifier 
further amplifies the integrator-output voltage to a 
level sufficient to drive the positive-negative level-
sensing differential comparators. These comparators, 
which sense imbalance conditions of the amplifier's 
output, provide demand for metered charge nulling 
of the input integrator at an injection rate determined 
by a local clock. 
Whenever the null amplifier produces an output 
voltage, the differential comparators sense the 
polarity or intensity of imbalance. Two of these com-
parators sense small (+) and (-) amplifier-output 
base-line shifts, while the third senses a level high 
enough to indicate the presence of a real event. The 
(+) and (-) comparators are triggered as the output 
base line moves either positively or negatively to pro-
duce a demand for continual nulling of the amplifier's 
base line.
The true numerical value transferred into the mem-
ory is the difference between thenumber of impulses 
originating from the (+) and (-) injectors during the 
sampling interval. This provides for true signal-averag-
ing over a fixed time period (integration), and allows 
for accurate assessment of the true zero. In between 
occurrences of events, the (+) and (-) comparators 
supply a metered feedback stabilization for the null-
seeking system by subtracting or adding charge to the 
integrator's input on demand, in order to maintain a 
zero amplifier-output voltage balance (differentiation). 
Notes: 
1.This information may interest designers of nuclear-
instrumentation or computer systems. 
2. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B69- 10640 
Source: W. W. Goldsworthy of 
Lawrence Radiation Laboratory
under contract to

Argonne National Laboratory 
(ARG- 10503) 
Patent status: 
Inquiries concerning rights for commercial use of 
this innovation may be addressed to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439
. 
.-
Brief 69-10640	 Category 01


Pulse-height analyzer with digital readout

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