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Photodetectors
Published in Robert G. Hunsperger, Photonic Devices and Systems, 2017
As larger reverse bias is applied to the device, the capacitance drops and the device i-layer is eventually depleted of carriers. For the device in Fig. 11, the rate of change slows at a voltage of about 5 V and a capacitance value of 85 fF. As the voltage continues to be increased, the capacitance approaches the number calculated using the parallel-plate approximation of 71 fF. For the maximum speed of response, the device should be operated at >5 V, where the capacitance is slowly changing versus bias. Minimizing capacitance for a pin photodetector means minimizing the device active area and using a thick, low-doped i-layer. The RC time constant of the device, series resistance times capacitance, is central in determining the frequency response of the device. This must be traded off against the increased carrier transit time due to a thicker i-layer (see Section I.C.7).
Bricks and Mortar: Micro/Nanoelectronics Fabrication
Published in John D. Cressler, Silicon Earth, 2017
RC clearly has dimensions of time (the exponential function is dimensionless). Hence, the smaller RC is, the faster we can charge the capacitor to the needed charge or voltage (this might represent our logical “1” for a digital bit moved from point A to point B). In fact, we can easily show that within one “RC time constant” the charge on the capacitor reaches (1 – e−1 = 63%) of its final value. Got it? Good.
Electric Circuits and Components
Published in Quamrul H. Mazumder, Introduction to Engineering, 2018
Similarly, for discharging a capacitor, you need a load connected in series, as shown in Figure 8.4e. The RC time constant refers to the amount of time needed for the capacitor to discharge 36.8% of supply voltage. Table 8.4 shows the capacitor discharge percentages for five time constant intervals. Figure 8.4g shows the timing diagram for a capacitor charging and discharging, and the equations are given as follows:
High-temperature LTCC assembly and design of SiC BJT-based negative charge pump
Published in International Journal of Electronics Letters, 2022
Sajib Roy, Khandokar Asif Faruque, Affan Abbasi, Alan Mantooth
The fabricated oscillator circuit schematic and the die micrograph are shown in Figure 4(b). The architecture is similar to the conventional astable multivibrator described in (Chang, 1970). The collector nodes of transistors Q3 and Q4 are cross-coupled to the base node via capacitors C3 and C4. The cross-coupled connection alternate charging and discharging of C3 and C4, creating the oscillating signals, at nodes OUT1 and OUT2, of the opposite phase. The VCTRL node connects to the base of Q3 and Q4 via resistors R2 and R3. Both R2 and R3 are on-chip resistors, valued at 10 kΩ to provide 100 µA of base current at room-temperature with the VCTRL set to 4 V. The VCTRL node provides frequency tuning capability by controlling the base current delivered to Q3/Q4. Resistors R1 and R4 are also on-chip (valued at 10 kΩ) and are connected to the VCC node. High valued resistors were avoided due to the low sheet resistance of the collector resistors. The output frequency of the oscillator depends on the RC time constant value of R1/R4 and C3/C4.
An Electronically Controllable Fractional Multivibrator
Published in IETE Journal of Research, 2021
İbrahim Ethem Saçu, Mustafa Alçı
The basic theory and design equations of fractional-order sinusoidal oscillators for two or three fractional capacitors are introduced in [4]. Different fractional-order sinusoidal oscillators based on two fractional capacitors are proposed where operational transresistance amplifiers (OTRA) and differential voltage current conveyors (DVCC) used as active building blocks [11, 12]. An analysis of general fractional oscillator topology based on two-port network is presented in [13]. Design and analysis of three or more fractional capacitors-based oscillators for multi-phases are reported in [14–16]. On the other hand, an examination of a fractional relaxation oscillator is given in [17]. The oscillation frequency in fractional oscillators depends on not only RC time constant but also fractional-order α. Therefore, fractional oscillators provide extra freedom of design.
Opto-electronic characterization of third-generation solar cells
Published in Science and Technology of Advanced Materials, 2018
Martin Neukom, Simon Züfle, Sandra Jenatsch, Beat Ruhstaller
The analytical approach is based on a simple model that considers one charge carrier type to be mobile and the other one to be static. The initial distribution of the charges is considered to be uniform in the bulk and diffusion is neglected. As these approximations are usually inadequate to describe thin film devices, it is apparent that the charge carrier mobility determined based on this model is less accurate compared to full drift-diffusion parameter extraction. In a previous publication, we have studied the CELIV experiment in detail and concluded that the formula (Equation (9)) obtains the charge carrier mobility with an accuracy of a factor of 4. The RC-effects lead to a strong underestimation of the mobility [55]. In such a case, it is advised to increase the thickness of the transparent conducting oxide (TCO) and metallize the TCO stripes. This effectively reduces the series resistance and thereby the RC time constant. Furthermore, it is advised to use devices with a small area leading to a small capacitance and a low RC time.