X-ray detector
An X-ray detector includes a first circuit with an NPN-type bipolar transistor and a second circuit configured to compare a voltage at a terminal of the NPN-type bipolar transistor with a reference value substantially equal to a value of the terminal voltage which would occur when the first circuit has been exposed to a threshold quantity of X-rays.
1. An X-ray detector, comprising:
a first circuit comprising a first NPN-type bipolar transistor; and
a second circuit configured to compare a voltage of the first circuit with a reference value substantially equal to a value of said voltage which would occur when the first circuit has received a threshold quantity of X-rays;
wherein the first circuit is configured so that a base voltage of the first NPN-type bipolar transistor is, during the operation of the detector, within a range of values for which a gain of the first NPN-type bipolar transistor having received no X-rays is at least 1.5 times greater than the gain of the first NPN-type bipolar transistor having received the threshold quantity of X-rays.
2. The detector according to claim 1 , wherein said voltage is a voltage at one of the terminals of the first NPN-type bipolar transistor.
3. The detector according to claim 2 , wherein said one of the terminals is an emitter of the first NPN-type bipolar transistor.
4. The detector according to claim 1 , wherein said voltage is substantially constant during the operation of the device in the absence of X-rays.
5. An X-ray detector, comprising:
a first circuit comprising a first NPN-type bipolar transistor; and
a second circuit configured to compare a voltage of the first circuit with a reference value substantially equal to a value of said voltage which would occur when the first circuit has received a threshold quantity of X-rays;
wherein the threshold quantity of X-rays is 10 grays.
6. The detector according to claim 5 , wherein said voltage is a voltage at one of the terminals of the first NPN-type bipolar transistor.
7. The detector according to claim 6 , wherein said one of the terminals is an emitter of the first NPN-type bipolar transistor.
8. The detector according to claim 5 , wherein said voltage is substantially constant during the operation of the device in the absence of X-rays.
9. An X-ray detector, comprising:
a first circuit comprising a first NPN-type bipolar transistor; and
a second circuit configured to compare a voltage of the first circuit with a reference value substantially equal to a value of said voltage which would occur when the first circuit has received a threshold quantity of X-rays;
wherein the first circuit is configured so that a voltage at a base of the first NPN-type bipolar transistor is, during the operation of the detector, within a range of values for which a gain difference between the first NPN-type bipolar transistor having received no X-rays and the first NPN-type bipolar transistor having received the threshold quantity of X-rays is greater than 10.
10. An X-ray detector, comprising:
a first circuit comprising two branches, a first branch comprising a first transistor and a first NPN-type bipolar transistor coupled in series, and a second branch comprising a second transistor and a second NPN-type bipolar transistor coupled in series, the first and second transistors being coupled as a current mirror so that the currents flowing through the first and second NPN-type bipolar transistors are substantially equal; and
a second circuit configured to compare a voltage of the first circuit with a reference value substantially equal to a value of said voltage which would occur when the first circuit has received a threshold quantity of X-rays.
11. The detector according to claim 10 , wherein bases of the first and second NPN-type bipolar transistors are coupled by a resistor.
12. The detector according to claim 11 , wherein the base of each of the first and second NPN-type bipolar transistors is coupled to a node of application of a reference voltage by a resistor.
13. The detector according to claim 10 , wherein a collector of the second NPN-type bipolar transistor is coupled to the base of the first NPN-type bipolar transistor through a unity gain amplifier circuit.
14. The detector according to claim 10 , wherein said voltage is a voltage at one of the terminals of the first NPN-type bipolar transistor.
15. The detector according to claim 14 , wherein said one of the terminals is an emitter of the first NPN-type bipolar transistor.
16. The detector according to claim 10 , wherein said voltage is substantially constant during the operation of the device in the absence of X-rays.
17. The detector according to claim 10 , wherein the threshold quantity of X-rays is 10 grays.
18. An X-ray detector, comprising:
a first circuit comprising a first NPN-type bipolar transistor; and
a second circuit configured to compare a voltage of the first circuit with a reference value substantially equal to a value of said voltage which would occur when the first circuit has received a threshold quantity of X-rays; and
a voltage generator circuit configured to generate the reference value comprising a third transistor in series with at least one resistor and at least one capacitor.
19. The detector according to claim 18 , further comprising a first transistor coupled in series with the first NPN-type bipolar transistor, and wherein the third transistor is coupled as a current mirror with the first transistor.
20. The detector according to claim 18 , further comprising a second transistor and a second NPN-type bipolar transistor coupled in series, and wherein the third transistor is coupled as a current mirror with the second transistor.
21. The detector according to claim 18 , wherein said voltage is a voltage at one of the terminals of the first NPN-type bipolar transistor.
22. The detector according to claim 21 , wherein said one of the terminals is an emitter of the first NPN-type bipolar transistor.
23. The detector according to claim 18 , wherein said voltage is substantially constant during the operation of the device in the absence of X-rays.
24. The detector according to claim 18 , wherein the threshold quantity of X-rays is 10 grays.
25. An X-ray detection method, comprising:
comparing a voltage of a first electronic circuit comprising a first NPN-type bipolar transistor with a reference value;
wherein the reference value is substantially equal to a value of said voltage which would occur when the first electronic circuit has received a threshold quantity of X-rays;
generating an output signal indicative X-ray exposure if the comparison is satisfied; and
applying a base voltage to the first NPN-type bipolar transistor that is within a range of values for which a gain of the first NPN-type bipolar transistor having received no X-rays is at least 1.5 times greater than the gain of the first NPN-type bipolar transistor having received the threshold quantity of X-rays.
26. The method according to claim 25 , wherein said voltage is a voltage on one of the terminals of the first NPN-type bipolar transistor.
27. The method according to claim 26 , wherein said one of the terminals is an emitter of the first NPN-type bipolar transistor.
28. The method according to claim 26 , wherein said voltage is substantially constant during the operation in the absence of X-rays.
29. The method according to claim 26 , wherein the threshold quantity of X-rays is 10 grays.
30. An X-ray detection method, comprising:
comparing a voltage of a first electronic circuit comprising a first NPN-type bipolar transistor with a reference value;
wherein the reference value is substantially equal to a value of said voltage which would occur when the first electronic circuit has received a threshold quantity of X-rays; and
generating an output signal indicative X-ray exposure if the comparison is satisfied; and
applying a voltage at the base of the first NPN-type bipolar transistor that is within a range of values for which a gain difference between the first NPN-type bipolar transistor having received no X-rays and the first NPN-type bipolar transistor having received the threshold quantity of X-rays is greater than 10.
31. The method according to claim 30 , wherein said voltage is a voltage on one of the terminals of the first NPN-type bipolar transistor.
32. The method according to claim 31 , wherein said one of the terminals is an emitter of the first NPN-type bipolar transistor.
33. The method according to claim 31 , wherein said voltage is substantially constant during the operation in the absence of X-rays.
34. The method according to claim 30 , wherein the threshold quantity of X-rays is 10 grays.