Because of the increasing in power density of electronic devices for medium and high power application, reliabilty of these devices is of great interest. Understanding the avalanche behaviour of a power device has become very important in these last years because it gives an indication of the maximum energy ratings which can be seen as an index of the device ruggedness. A good description of this behaviour is given by the static IV blocking characteristc. In order to avoid self heating, very relevant in high power devices, very short pulses of current have to be used, whose value can change from few milliamps up to tens of amps. The most used method to generate short pulses is the TLP (Transmission Line Pulse) test, which is based on charging the equivalent capacitance of a transmission line to high value of voltage and subsequently discharging it onto a load. This circuit let to obtain very short square pulses but it is mostly used for evaluate the ESD capability of semiconductor and, in this environment, it generates pulses of low amplitude which are not high enough to characterize the avalanche behaviour of high power devices . Advanced TLP circuit able to generate high current are usually very expensive and often suffer of distorption of the output pulse. In this article is proposed a simple, low cost circuit, based on a boosted-TLP configuration, which is capable to produce very square pulses of about one hundreds of nanosecond with amplitude up to some tens of amps. A prototype is implemented which can produce pulses up to 20A of amplitude with 200 ns of duration which can characterize power devices up to 1600V of breakdown voltage. Usage of microcontroller based logic make the circuit very flexible. Results of SPICE simulation are provided, together with experimental results. To prove the effectiveness of the circuit, the I-V blocking characteristics of two commercial devices, namely a 600V PowerMOS and a 1200V Trench-IGBT, are measured at different operating temperature.
The Drever-Pound-Hall technique is a powerful tool to stabilize the laser frequency or to lock a cavity to a laser by controlling its length in the order of fraction of wavelength1-3 . It had been widely applied as method to interrogate fiber optical cavity based sensors, as strain sensors or refractive index sensors, since it allows to reach very high sensitivity, especially in dynamic range, only theoretically limited by the laser shot noise4-7 . In this paper we present a detailed analysis on the possibility to use the DPH technique for the simultaneous detection of detuning of two or more cavities each lying on a different output branch of a splitter, by interrogating them using only the single input channel of the splitter. More precisely, starting from a reflection configuration of the present technique, where the error signal to control the cavity length is extracted by the signal reflected by the cavity, we analyze all the possible configurations to simultaneously interrogate and discriminate the different cavities, using the same input channel to have not overlap and interference between the signals reflected by each of them. The interest of this kind of analysis resides in the possibility to design very compact and less invading sensors that requires bidirectional detection of the involved physical quantity or, the simultaneous and independent control of several parameters (like, for example, bidirectional strain sensors, that simultaneously detect the strain along two orthogonal directions, or magnetic field sensor able to determine the intensity of the field along perpendicular directions, or, refractive index sensor temperature calibrated8 ). Using a single interrogation/detection channel the sensor can be placed far away from the interrogation/detection apparatus and connected to the latest only by means of a single optical fiber, instead to have more signal detection channels.
A silicon photomultiplier (SiPM) is a matrix of Geiger-mode avalanche photodiodes (GM-APDs) connected in parallel.
One of the main drawback in the SiPm is the low Photon Detection Efficiency(PDE) also due to the low geometrical fill
factor of the microcells array. This paper reports on the analysis and simulation of the single floating field ring
technique, applied to the junction termination of the single cell of a Silicon Photomultiplier (SiPm). A floating guard ring
is made along the border of the single microcell and it is not connected to the cathodic contact. Even if the ring is not
electrically connected to the main junction, it mitigates the variation of the electrical field at the main termination. The
effect of the junction-to-ring distance is analytically investigated by using cylindrical coordinates and an optimal
distance together with the optimal width is found. Results show that the single floating ring reduces the junction edge
electric field by keeping constant the size of the microcell allowing, then, an improvement for the geometrical fill factor.
Results are supported by TCAD simulations.
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