DE4201021A1

DE4201021A1 - Circuit for measuring small currents in semiconductors with leakage current compensation - contains tapping point with artificially raised potential achieved via one or more PN junctions

Info

Publication number: DE4201021A1
Application number: DE19924201021
Authority: DE
Inventors: Hans Dipl Phys Schoefer
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-01-16
Filing date: 1992-01-16
Publication date: 1993-07-22

Abstract

The circuit taps the leakage currents (IL,IB) via one or more electronic components (DV) acting as signal transducers at an artificially high potential. The potential at the tapping point is raised by the PN junction of one or more semiconductors. A photodiode in conjunction with x-ray signal amplifying material can be used as the signal transducer. USE/ADVANTAGE - The arrangement enables the sensitivity of radiation measurement devices with semiconducting detectors to be increased by more than 100 times. Semiconductor detector can be for computer tomography, X-ray exposure appts., X-ray beam measurement appts., dosimeter or photometer.

Description

Die Erfindung betrifft die Steigerung der Empfind lichkeit von Meßeinrichtungen mit Halbleiterdetektoren durch eine Schaltung aus elektronischen Bauelementen, die geeignet ist signalinduzierte Ströme von Leck strömen (Rauschen - elektromagnetische Einstreuungen) zu trennen. Gleichzeitig wird durch schaltungstechni sche Maßnahmen erreicht, daß der zeitliche Verlauf der Leckströme zum Meßzeitpunkt als zusätzliche Information zur Steigerung der Meßgenauigkeit zur Verfügung steht.The invention relates to increasing sensitivity possibility of measuring devices with semiconductor detectors through a circuit of electronic components, which is suitable for signal-induced leakage currents flow (noise - electromagnetic interference) to separate. At the same time through circuit technology cal measures achieved that the temporal course the leakage currents at the time of measurement as additional Information to increase the accuracy of measurement Available.

Durch Anwendung der Schaltung werden Empfindlich keitssteigerungen z. B. an Strahlenmeßgeräten um einen beträchtlichen Faktor (<100-fach) verwirklicht. Die Empfindlichkeitsbereiche, die durch Anwendung der schaltungstechnischen Maßnahme erreicht werden, sind Meßeinrichtungen, die mit Halbleiterdetektoren aus gestattet sind, bisher nicht zugänglich.By using the circuit become sensitive increases in z. B. on radiation meters around considerable factor (<100 times) realized. The sensitivity ranges, which are applied by the circuit measure are achieved Measuring devices made with semiconductor detectors are not yet accessible.

Die Lösung der Aufgabe, Steigerung der Empfindlichkeit von Meßsystemen mit Halbleiterdetektoren, erfolgt durch eine elektronische Schaltung, die mit n Einzeldedektoren (n 1) so verknüpft ist, daß der Leckstrom der Einzel detektoren abgeführt wird, bevor das Nutzsignal (z. B. strahleninduziertes Signal) einem Meß-Netzwerk zuge führt wird.The solution to the problem, increasing sensitivity of measuring systems with semiconductor detectors, is carried out by an electronic circuit with n individual detectors (n 1) is linked so that the leakage current of the individual detectors is removed before the useful signal (e.g. radiation-induced signal) a measurement network leads.

Die Abführung des Leckstroms IL des Detektors D erfolgt als Leckstrom dem Detektor artverwandter Bauelemente IB an der direkt dem Detektor nachgeschalteten Konstant spannungsquelle UQ. Als Maß für den Signalstrom IS steht die Spannung UA an dem Arbeitswiderstand RA an und kann von einem Spannungsmeßnetzwerk der Auswertung zugeführt werden.The leakage current IL of the detector D is dissipated as leakage current to the detector of related components IB at the constant directly downstream of the detector voltage source UQ. As a measure of the signal current IS the voltage UA at the load resistor RA and can fed from a voltage measurement network for evaluation will.

Damit die Schaltung den gewünschten Effekt erzielt, müssen folgende Bedingungen eingehalten werden:So that the circuit achieves the desired effect, the following conditions must be met:

1. IL + Epsilon = IB where Epsilon is about size should correspond to the signal to be measured and at all working temperatures of the measuring device <0 have to be.
2. UQ »UA
3. UQ <UV where UV is the supply voltage of the Measuring system is.

Zur Stabilisierung der Detektorschaltung dient der Mehrebenenschalter S, der beim Abschalten der Meß einrichtung das am Detektor während der Messung vorhandene Potential aufrechterhält.The stabilizes the detector circuit Multi-level switch S, which when switching off the measuring device on the detector during the measurement maintains existing potential.

In Ausführungsformen der Erfindung kann das Detektor signal das Signal von Photodioden aus Silizium sein und als artverwandte Bauelemente Siliziumdioden ver wendet werden. Als Konstantspannungsquelle kann der PN-Übergang eines Halbleiters, der in Fluß-Richtung geschaltet ist, verwendet werden.In embodiments of the invention, the detector signal be the signal from silicon photodiodes and ver as related components silicon diodes be applied. As a constant voltage source, the PN junction of a semiconductor in the flow direction is used.

Die Erfindung wird im folgenden anhand der Schaltung eines Ausführungsbeispiels beschrieben:The invention is based on the circuit described an exemplary embodiment:

Im Eingangskreis des Dosismeßgerätes QUART-dido/fluory der Firma QUART ist zwischen die Signalleitung des Detektors und den Meßeingang eines Operationsverstärkers die Emitter-Basis-Diode eines Transistors (TR) des Typs BC 238 geschaltet. Auf der Basis-Seite des Transistors ist an der Photodiode DS der Meßsonde in thermischer Nachbar schaft eine Si-Diode des Typs 1N 4146 in Sperrichtung gegen Masse geschaltet. An dem Arbeitswiderstand von 20 Mohm der dem Transistor nach geschaltet ist, wird über den pos. Eingang des Operationsverstärkers AD 548 das Signal dem Auswertegerät zugeführt.In the input circuit of the dose meter QUART-dido / fluory from QUART is between the Signal line of the detector and the measurement input of an operational amplifier, the emitter-base diode of a transistor (TR) of the BC 238 type. On the base side of the transistor is on the Photodiode DS of the measuring probe in a thermal neighbor shafts an Si diode of the type 1N 4146 in the reverse direction switched to ground. At the working resistance of 20 Mohm which is connected after the transistor about the pos. Input of the operational amplifier AD 548 the signal is fed to the evaluation device.

Bei dem vorliegenden Gerät ist die Anzeigegenauigkeit des Signalstroms 1Exp-12 A. Dabei ist die Höhe des abgeführten Leckstroms etwa 1Exp-9 A. Der zulässige Temperaturbereich liegt zwischen 5°C und 50°C.In the present device, the display accuracy is of the signal current 1Exp-12 A. The height of the dissipated leakage current about 1Exp-9 A. The permissible Temperature range is between 5 ° C and 50 ° C.

RA Arbeitswiderstand
TR Transistor
D Signalgeber
DV dem Signalgeber artverwandtes Bauelement
OP Operationsverstärker
UQ Spannung an Basis und Kollektor des Transistors
UA Spannung am Arbeitswiderstand
IL Leckstrom von D
IB Leckstrom von DV
IS Signalstrom
S Schalter (2 Ebenen)
R Spannungsteiler zur Festlegung des Potentials bei ausgeschaltetem GerätRA working resistance
TR transistor
D signal generator
DV component related to the signal generator
OP operational amplifier
UQ voltage at the base and collector of the transistor
UA voltage at load resistance
IL leakage current from D
IB leakage current from DV
IS signal current
S switch (2 levels)
R Voltage divider to determine the potential when the device is switched off

Claims

1. Circuit for measuring small currents with compensation for leakage currents characterized in that leakage currents are derived at one point artificially increased potential via one or more electronic components related to the signal generator.

2. Circuit according to claim 1 or one of the following characterized in that the increase in Potential at the derivation point through the PN junction of a semiconductor is generated.

3. Circuit according to claim 1 or one of the following characterized in that the increase in Potential at the derivation point through the PN transitions several semiconductors is generated.

4. Circuit according to claim 1 or one of the following characterized in that as a signal generator Photodiode in connection with X-ray signal amplifier materials are used.

5. Circuit according to claim 1 or one of the following characterized in that as a signal generator Photodiode is used.

6. Circuit according to claim 1 or one of the following characterized in that the leakage current of the on slave components in the area of use never smaller is than the leakage current to derive this Current component used.

7. Circuit according to claim 1 or one of the following characterized in that the signal pick-up Component and the structure that derives the leakage current element are thermally coupled.

8. Circuit according to claim 1 or one of the following characterized in that the signal generator and the Components of the circuit even when switched off Condition kept at a fixed potential will.

9. Circuit according to claim 1 or one of the following characterized in that the signal generator Semiconductor detector for use in a computer is tomograph.

10. Circuit according to claim 1 or one of the following characterized in that the signal generator Semiconductor detector for use in an exposure automatic processing of an X-ray recording device is.

11. Circuit according to claim 1 or one of the following characterized in that the signal generator Semiconductor detector for use in an exposure automatic processing of an X-ray fluoroscopy device is.

12. Circuit according to claim 1 or one of the following characterized in that the signal generator Semiconductor detector for use as a measuring probe in an X-ray meter z. B. a dosimeter is.

13. Circuit according to claim 1 or one of the following characterized in that the signal generator Semiconductor detector for use as a measuring probe in a light meter z. B. is a photometer.

14. Circuit according to claim 1 or one of the following characterized in that the generation of the increased potential serving component and that Signaling device and that for compensation used component parts of a common can be the same integrated circuit.