| 1. |
- Hedayati, Raheleh, et al.
(författare)
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A 500 degrees C 8-b Digital-to-Analog Converter in Silicon Carbide Bipolar Technology
- 2016
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Ingår i: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 63:9, s. 3445-3450
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Tidskriftsartikel (refereegranskat)abstract
- High-temperature integrated circuits provide important sensing and controlling functionality in extreme environments. Silicon carbide bipolar technology can operate beyond 500 degrees C and has shown stable operation in both digital and analog circuit applications. This paper demonstrates an 8-b digital-to-analog converter (DAC). The DAC is realized in a current steering R-2R configuration. High-gain Darlington current switches are used to ensure ideal switching at 500 degrees C. The measured differential nonlinearity (DNL) and integral nonlinearity (INL) at 25 degrees C are 0.79 and 1.01 LSB, respectively, while at 500 degrees C, the DNL and INL are 4.7 and 2.5 LSB, respectively. In addition, the DAC achieves 53.6 and 40.6 dBc of spurious free dynamic range at 25 degrees C and 500 degrees C, respectively.
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| 2. |
- Hedayati, Raheleh, et al.
(författare)
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A Monolithic, 500 degrees C Operational Amplifier in 4H-SiC Bipolar Technology
- 2014
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Ingår i: IEEE Electron Device Letters. - : IEEE. - 0741-3106 .- 1558-0563. ; 35:7, s. 693-695
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Tidskriftsartikel (refereegranskat)abstract
- A monolithic bipolar operational amplifier (opamp) fabricated in 4H-SiC technology is presented. The opamp has been used in an inverting negative feedback amplifier configuration. Wide temperature operation of the amplifier is demonstrated from 25 degrees C to 500 degrees C. The measured closed loop gain is around 40 dB for all temperatures whereas the 3 dB bandwidth increases from 270 kHz at 25 degrees C to 410 kHz at 500 degrees C. The opamp achieves 1.46 V/mu s slew rate and 0.25% total harmonic distortion. This is the first report on high temperature operation of a fully integrated SiC bipolar opamp which demonstrates the feasibility of this technology for high temperature analog integrated circuits.
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| 3. |
- Hedayati, Raheleh, 1984-
(författare)
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High-Temperature Analog and Mixed-Signal Integrated Circuits in Bipolar Silicon Carbide Technology
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Silicon carbide (SiC) integrated circuits (ICs) can enable the emergence of robust and reliable systems, including data acquisition and on-site control for extreme environments with high temperature and high radiation such as deep earth drilling, space and aviation, electric and hybrid vehicles, and combustion engines. In particular, SiC ICs provide significant benefit by reducing power dissipation and leakage current at temperatures above 300 °C compared to the Si counterpart. In fact, Si-based ICs have a limited maximum operating temperature which is around 300 °C for silicon on insulator (SOI). Owing to its superior material properties such as wide bandgap, three times larger than Silicon, and low intrinsic carrier concentration, SiC is an excellent candidate for high-temperature applications. In this thesis, analog and mixed-signal circuits have been implemented using SiC bipolar technology, including bandgap references, amplifiers, a master-slave comparator, an 8-bit R-2R ladder-based digital-to-analog converter (DAC), a 4-bit flash analog-to-digital converter (ADC), and a 10-bit successive-approximation-register (SAR) ADC. Spice models were developed at binned temperature points from room temperature to 500 °C, to simulate and predict the circuits’ behavior with temperature variation. The high-temperature performance of the fabricated chips has been investigated and verified over a wide temperature range from 25 °C to 500 °C. A stable gain of 39 dB was measured in the temperature range from 25 °C up to 500 °C for the inverting operational amplifier with ideal closed-loop gain of 40 dB. Although the circuit design in an immature SiC bipolar technology is challenging due to the low current gain of the transistors and lack of complete AC models, various circuit techniques have been applied to mitigate these problems. This thesis details the challenges faced and methods employed for device modeling, integrated circuit design, layout implementation and finally performance verification using on-wafer characterization of the fabricated SiC ICs over a wide temperature range.
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| 4. |
- Hedayati, Raheleh, 1984-, et al.
(författare)
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High Temperature Bipolar Master-Slave Comparator and Frequency Divider in 4H-SiC Technology
- 2017
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Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 897, s. 681-684
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Tidskriftsartikel (refereegranskat)abstract
- This paper demonstrates a fully integrated master-slave emitter-coupled logic (ECL)comparator and a frequency divider implemented in 4H-SiC bipolar technology. The comparator consists of two latch stages, two level shifters and an output buffer stage. The circuits have been tested up to 500 °C. The single ended output swing of the comparator is -7.73 V at 25 °C and-7.63 V at 500 °C with a -15 V supply voltage. The comparator consumes 585 mW at 25 °C. The frequency divider consisting of two latches shows a relatively constant output voltage swing over the wide temperature range. The output voltage swing is 7.62 V at 25 °C and 7.32 V at 500 °C.
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| 5. |
- Hedayati, Raheleh, et al.
(författare)
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Material aspects of wide temperature range amplifier design in SiC bipolar technologies
- 2016
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Ingår i: Journal of Materials Research. - : Cambridge University Press. - 0884-2914 .- 2044-5326. ; 31:19, s. 2928-2935
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) is the main semiconductor alternative for low loss high voltage devices. The wide energy band gap also makes it suitable for extreme environment electronics, including very high temperatures. Operating integrated electronics at 500-600 °C poses several materials challenges. However, once electronics is available for these high temperatures, the added challenge is designing integrated circuits capable of operating in the entire range from room temperature to 500 °C. Circuit designers have to take into account parameter variations of resistors and transistors, and models are needed for several temperatures. A common circuit design technique to manage parameter variations between different transistors, without wide temperature variations, is to use negative feedback in amplifier circuits. In this paper we show that this design technique is also useful for adapting to temperature changes during operation. Two different amplifier designs in SiC are measured and simulated from room temperature up to 500 °C.
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| 6. |
- Hedayati, Raheleh, et al.
(författare)
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Wide Temperature Range Integrated Amplifier in Bipolar 4H-SiC Technology
- 2016
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Ingår i: 2016 46TH EUROPEAN SOLID-STATE DEVICE RESEARCH CONFERENCE (ESSDERC). - : IEEE. - 9781509029693 ; , s. 198-201
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Konferensbidrag (refereegranskat)abstract
- This paper presents a high temperature integrated amplifier implemented in bipolar 4H-SiC technology. A 40 dB negative feedback voltage amplifier has been designed using the structured design method to overcome the temperature variation of device parameters. The amplifier performance degrades as the temperature increases from room temperature up to 500 degrees C. The measured gain is reduced from 39 dB at room temperature to 34 dB at 500 degrees C, and the 3-dB bandwidth decreases from 195 kHz to 100 kHz. The measured power-supply-rejection-ratio (PSRR) is reduced from -78 dB to -62 dB, while the output voltage swing decreases from 8 V to 7 V.
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| 7. |
- Hedayati, Raheleh, et al.
(författare)
-
Wide Temperature Range Integrated Bandgap Voltage References in 4H–SiC
- 2016
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Ingår i: IEEE Electron Device Letters. - : IEEE. - 0741-3106 .- 1558-0563. ; 37:2, s. 146-149
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Tidskriftsartikel (refereegranskat)abstract
- Three fully integrated bandgap voltage references (BGVRs) have been demonstrated in a 4H-SiC bipolar technology. The circuits have been characterized over a wide temperature range from 25 degrees C to 500 degrees C. The three BGVRs are functional and exhibit 46 ppm/degrees C, 131 ppm/degrees C, and 120 ppm/degrees C output voltage variations from 25 degrees C up to 500 degrees C. This letter shows that SiC bipolar BGVRs are capable of providing stable voltage references over a wide temperature range.
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| 8. |
- Shakir, Muhammad, et al.
(författare)
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Electrical characterization of integrated 2-input TTL NAND Gate at elevated temperature, fabricated in bipolar SiC-technology
- 2018
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Ingår i: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017. - : Trans Tech Publications Inc.. - 9783035711455 ; , s. 958-961
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Konferensbidrag (refereegranskat)abstract
- This work presents the design and electrical characterization of in-house-fabricated 2-input NAND gate. The monolithic bipolar 2-input NAND gate employing transistor-transistor logic (TTL) is demonstrated in 4H-SiC and operates over a wide range of temperature and supply voltage. The fabricated circuit was characterized on the wafer by using a hot-chuck probe-station from 25 °C up to 500 °C. The circuit is also characterized over a wide range of voltage supply i.e. 11 to 20 V. The output-noise margin high (NMH) and output-noise margin low (NML) are also measured over a wide range of temperatures and supply voltages using voltage transfer characteristics (VTC). The transient response was measured by applying two square waves of, 5 kHz and 10 kHz. It is demonstrated that the dynamic parameters of the circuit are temperature dependent. The 2-input TTL NAND gate consumes 20 mW at 500 °C and 15 V.
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| 9. |
- Shakir, Muhammad, et al.
(författare)
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Towards Silicon Carbide VLSI Circuits for Extreme Environment Applications
- 2019
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Ingår i: Electronics. - : MDPI AG. - 2079-9292. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- A Process Design Kit (PDK) has been developed to realize complex integrated circuits in Silicon Carbide (SiC) bipolar low-power technology. The PDK development process included basic device modeling, and design of gate library and parameterized cells. A transistor–transistor logic (TTL)-based PDK gate library design will also be discussed with delay, power, noise margin, and fan-out as main design criterion to tolerate the threshold voltage shift, beta (β) and collector current (IC) variation of SiC devices as temperature increases. The PDK-based complex digital ICsdesign flow based on layout, physical verification, and in-house fabrication process will also be demonstrated. Both combinational and sequential circuits have been designed, such as a 720-device ALU and a 520-device 4 bit counter. All the integrated circuits and devices are fully characterized up to 500 °C. The inverter and a D-type flip-flop (DFF) are characterized as benchmark standard cells. The proposed work is a key step towards SiC-based very large-scale integrated (VLSI) circuits implementation for high-temperature applications.
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| 10. |
- Tian, Ye, et al.
(författare)
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SiC BJT Compact DC Model With Continuous- Temperature Scalability From 300 to 773 K
- 2017
-
Ingår i: IEEE Transactions on Electron Devices. - : IEEE. - 0018-9383 .- 1557-9646. ; 64:9, s. 3588-3594
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Tidskriftsartikel (refereegranskat)abstract
- The first vertical bipolar intercompany (VBIC)-based compact dc model has been developed and verified for a low-voltage 4H-SiC bipolar junction transistor to continuously map a wide temperature range from 300 to 773 K. Temperature and doping dependent physical models for bandgap, incomplete ionization, carrier mobility, and lifetime have been taken into account to give physically meaningful fitting parameters for the compact model. Isothermal simulations using the default VBIC model are performed to extract key parameter sets from measured data at seven different temperature points. Then new temperature dependent equations for the key parameters are proposed and embedded in the default VBIC model. Consequently, a single set of model parameters at 300 K is used to achieve fitting over a wide temperature range from 300 to 773 K. This new model can be used for simulating circuits that require continuous description of device dc performance over a wide temperature range.
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