TECHNICAL DATA. benefits

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1 benefits > Instant & direct, non-destructive reading of radiation dose > Zero or very low power consumption > Large dynamic range > Smallest active volume of all dosimeters > Easily integrated into an automated system 400 nm RADFET in 6L Plastic Package applications > Personal dosimetry for accidental irradiation > Dose monitoring for high-energy physics labs (such as synchrotron environments) > Dose monitoring in nuclear facilities > Radiation measurements in space > Radiotherapy description RADFET, a discrete p-channel MOSFET optimized for radiation sensitivity, is sensitive to ionizing radiation: gamma rays, X-rays and protons. The critical region of the RADFET is its gate oxide. Through generation and trapping of radiation-induced charges in the gate oxide, radiation exposure changes the threshold voltage of the RADFET; this change is related to the radiation dose. The read-out is done by forcing a D current (in the range of tens of μa) into the device and measuring the D voltage (in the range of calibration curve) is used to read the dose. RADFET is an integrating dosimeter; it measures absorbed radiation dose. The minimum detectable dose is 1cGy (1rad) and the maximum dose is typically 1kGy (100krad) or higher, depending on the application requirements.

2 part description and pin-out is a Tyndall RADFET chip, denoted OMRAD, packaged in a plastic SOT-23 six-lead package. This part consists of two identical p-channel MOSFETs/RADFETs (R1 and R2) and a diode (see Figure 1 and Table 1). The RADFET gate oxide thickness is 400 nm and W/L is 300 μm/ 50 μm. The two RADFETs have individual gate and drain terminals, while the source and bulk are common and connected together; this is also the diode bulk contact. Table 1: pin-out description. Pin Number Description 1 Diode 2 Source/Bulk (ommon) 3 Gate of R2 4 Gate of R1 5 Drain of R2 Figure 1: pin-out drawing. 6 Drain of R1 maximum ratings Table 2: Maximum ratings of the RADFET. haracteristics Symbols Specification Units Remarks Drain-Source Voltage V DS -25 V Gate-Source Voltage V GS +/- 50 V Drain-Gate Voltage V DG -50 V Drain urrent I D -1 ma ontinuous Source urrent I S -1 ma ontinuous Operating Temperature Range T op -20 to +70 o Storage Temperature Range T stg -40 to +85 o Soldering Termperature T sol +250 o 2 Document Revision: DS R1

3 modes of operation Irradiation Mode (Sense Mode) In this mode of operation it is recommended that all terminals of the RADFET are connected to ground. For alternative biasing options, contact the manufacturer. Read-Out Mode (Accumulated Radiation Dose Read-Out) The RADFET can be read at arbitrary intervals, depending on the application. The period between readings can be from seconds to days. The Reader ircuit (R), which is used to read out the RADFET, is shown in Figure 2 with connection configuration in Table 3. Table 3: onnections in Read-Out mode. Terminal S = B Bias urrent is forced (R_I) Voltage reading is taken (R_V) G = D 0V (common) Figure 2: Reader ircuit (R) configuration. urrent R_I is forced into the RADFET, connected in R configuration (Figure 2), for several hundred ms. The voltage at the source (R_V) is measured; this voltage is called "R threshold voltage". Typical I-V curve for the unirradiated device in this configuration is shown in Figure 3. In principle, any read-out current value (R_I) can be chosen, as long as the value remains unchanged after the start of radiation exposure. R_I values < 5 μa should be used only after consultation with the manufacturer. For best temperature compensation, an R_I value of 10 μa is recommended. Figure 3: Reader ircuit (R) typical I-V curve, pre-irradiation. 3 Document Revision: DS R1

4 electrical parameters The most important electrical parameter of un-irradiated RADFET is R threshold voltage (R_V). The specification for R_V is provided in Table 4. Results of R_V measurements prior to shipment are included in documentation that comes with ordered parts. Typically the range of R_V of delivered parts is significantly tighter than in the specification. Table 4: Specification for R threshold voltage. Parameter Symbol Test ircuit and onditions Limits Unit Min Max R Threshold Voltage R_V Figure 2 and Table 3 R_I = 10 μa V calibration data The calibration curve for the RADFET shows evolution of V (the change in R threshold voltage with respect to its pre-irradiation value) with dose. Note that a specific calibration curve is associated with each RADFET production batch. The curve will be provided in documentation supplied with ordered parts. For illustration, a typical calibration curve is shown in Figure 4. Figure 4: Typical calibration curve indicating change in R_V during irradiation. Note that in this case, all RADFET terminals are grounded during irradiation.. 4 Document Revision: DS R1

5 packaging information Table 5: package specifications. Description Package Type Specification Six-pin plastic SOT-23 package Package Dimensions (L x W x H) 2.90 mm x 2.80 mm x 1.10 mm (see Figure 5) Figure 5: package diagram. 5 Document Revision: DS R sales@ 2015 Tyndall Works. All rights reserved.