Data Communications - Wed, 27 Mar GMT PDF Cmos Current Mode Circuits For. Data Communications CMOS Current-Mode Circuits for Data. Communications Download Pdf, Free Pdf Cmos Current Mode Circuits For Data. Communications Download. Leakage Current In Sub-micrometer Cmos Gates. CMOS CURRENT MODE CIRCUITS FOR DATA COMMUNICATIONS cmos current mode circuits pdf. Complementary metal–oxide–semiconductor (CMOS) is a.
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Titles in Series: CMOS CURRENT-MODE CIRCUITS FOR DATA COMMUNICATIONS. Yuan, Fei. ISBN: RF POWER AMPLIFIERS FOR MOBILE. CMOS Current-Mode Circuits for Data Communications Digitally watermarked, DRM-free; Included format: PDF; ebooks can be used on all reading devices. Cmos Current Mode Circuits For Data Communications Reprint - [Free] Cmos Current. Mode Circuits Sun, 31 Mar GMT (PDF) Digital design.
Engineering, Kumaon Engineering College KEC , Dawarahat Almora , Uttarakhand ABSTRACT The performance of the data transmission using the principle of the optical communication can be enhanced further simply by increasing both the wavelength count and bit rate per channel, so as to improve the utilization of the optical fiber bandwidth. This approach in turn requires the most suitable device structures and the technologies for both opto-electronic transducers and the associated driving electronics circuitry. The number of transistor stages required between the power and ground rails is only two so that the minimum supply voltage required is one threshold voltage plus one pinch-off voltage. The pre-amplifier is a balanced two-stage configuration such that the effect of bias-dependent mismatches is minimized. A new inductive series-peaking technique has been introduced so as to enhance the bandwidth by utilizing the resonance characteristics of LC networks. In addition to this arrangement, a new negative differential current feedback technique has been put forward for the discussion so as to boost the bandwidth of the system and to reduce the value of peaking inductors. This pre-amplifier circuit has been implemented in TSMC 0.
On the other hand, the fabrication of strain compatible optical cavities was demonstrated for microdiscs 16 , 17 and also microbridges 28 , 29 , providing the experimental access to the above-mentioned quantities and to investigate the lasing 30 , The purpose of this paper is to study in detail a laser based on strained undoped germanium.
We report for strained Ge key lasing attributes such as an absolute power measurement demonstrating a high differential quantum efficiency when the laser operates above a sharp laser threshold as well as the onset of mode competition and linewidth narrowing. We argue that—for our case—lasing in Ge under pulsed excitation is helped by a non-equilibrium carrier distribution in k-space when the two valleys become closely aligned energetically.
This effect reveals the importance of directness for lasing and—in particular—for the lasing at higher operation temperature in any of the above-mentioned configurations. Results Strained germanium microbridges For this study, we investigated suspended Ge microbridges integrated into a strain preserving optical cavity with, at low temperature, uniaxially loaded tensile strain up to 5.
The strain is achieved by the relaxation of two biaxially pre-strained pads 14 , 22 , as shown in Fig. The corresponding strain values at 20 K 5. The thus deduced strain values are incorporated in Fig. The above-mentioned TB model, detailed in ref.
The crossover value is larger than the pseudo-potential calculation of ref. For comparison, the here employed tight-binding model predicts for the biaxial strain a crossing to the direct bandgap configuration around 2.
The geometry of the microbridge structure is defined by e-beam lithography and it is transferred to the Ge layer via inductively coupled plasma dry etching. The HF vapour selectively under etches the oxide, allowing the pads to relax their strain along the directions indicated by the red arrows, stretching the microbridge indicated by the red circle. The strain of the probed microbridge configurations L3, L4 and L5 at 20 K, namely 5.
For an empty cavity—i.
Throughout the paper, all the results are obtained from long cavity samples, if not explicitly stated otherwise. The microbridge structures were excited with two kinds of pump laser; a diode laser running in continuous wave CW and an optical parametric oscillator OPO operated in pulsed mode pulse width and repetition rate of ps and 83 MHz, respectively.
Both lasers run at energies below the bandgap of unstrained Ge, making the pad regions transparent for the excitations. The samples were mounted in a cryostat with a base temperature of 20 K, see Fig. The emission intensity is given as the averaged power harvested within the NA of the microscope. Lasing characteristics and quantum efficiency In Fig.
The strong periodic modulation of the intensity is attributed to the cavity modes evolving when the medium is driven to transparency by optical pumping. We obtain a strong emission from just few cavity modes revealing mode competition, whose appearance we attribute to stimulated emission and optical feedback and we consider it as one of the strongest evidences of lasing. This feature is missing in the steady state regime, where the emission pattern is largely independent on the excitation intensity and can be well explained by amplified spontaneous emission.
In grey colours are the photoluminescence PL spectra taken at about 4 mW excitation power, excited with a continuous wave CW diode laser operating at meV energy. In blue, orange and red the corresponding lasing spectra obtained when the excitation is switched to the pulsed regime, obtained from the tuneable OPO, at an average excitation power of 2 mW, with energy of meV and meV, for L4 and L3, L5 samples, respectively.
Per each sample, the relative magnification of the PL spectrum with respect to the corresponding laser spectrum is reported. Curves for different excitation energies are shown. Inset: threshold dependency on the excitation energy. The value of the differential efficiency, commonly referred to as slope efficiency, is indicated for the pump energy of meV.
Note that the reported linewidths are apodized and approaching the instrumental resolution of 0. By further decreasing the excitation energy, the emission intensity raises continuously up to the highest applied powers, but sub linearly with the excitation power.
The analysis of the pump photon energy dependence of the laser threshold power is shown in the inset of Fig. Overall, the threshold power is lowest 0. This resonance is also responsible for the presence of a Raman scattering gain that compete with inversion gain in this pump energy range This behaviour will be discussed more in detail elsewhere. For the excitation power of 0.
In order to avoid a numerical analyses of finite size effects, which are particularly important for the low energy excitations, the absorbed fraction for these energies is obtained from the experimental slope of the mode shifts 37 normalized to the absorbed fraction deduced for the meV excitation. Interestingly, parasitic intervalence band absorption—which is the main challenge for the doped Ge approach 20 —is at such low densities and the low temperatures strongly suppressed.
We also analysed the differential efficiency of an L5 sample, by converting the average excitation and the collected power of the light-in light-out curves of Fig. By mapping the Cassegrain geometry of our collecting optics to the computed far-field of the corner-cube structure see Supplementary Fig. The latter, together with the pumping efficiency factor, enables us to plot the inferred light-in light out of the structure, reported in Fig.
This high number, however, comes with a rather large uncertainty which we estimate to be about a factor of 2 as derives from the uncertainty of the set-up calibration, the alignment of the sample and the consequent error in the far-field collection estimation as well as the neglect of other scattering channels such as surface roughness in the 3D model.
Nevertheless, this high efficiency, when compared to the reported quantum efficiency for GeSn of about 1.
The spectral linewidth of the emitted spectrum as a function of pump power are compared for both continuous wave and pulsed powers in Fig. The linewidth measure in continuous wave is seen to decrease continuously as a function of pump intensity, reaching 0. However, the lack of clear threshold behaviour demonstrates that these devices do not operate in the true laser regime, but are simply exhibiting emission from high Q modes in an active region, which becomes increasingly transparent.
In contrast, the same devices operating in pulse operation exhibit a much narrower linewidth, down to 0. The narrowness of the lines, despite the transient nature of the excitation, indicates a well-developed laser operation.
Unfortunately, in pulsed excitation regime, the spectra could not be measured far below threshold because of the low duty cycle of the pumping and hence the lack of signal. Temperature dependence We furthermore investigate the temperature dependence of the laser characteristics. In Fig. The number of transistor stages required between the power and ground rails is only two so that the minimum supply voltage required is one threshold voltage plus one pinch-off voltage.
The pre-amplifier is a balanced two-stage configuration such that the effect of bias-dependent mismatches is minimized. A new inductive series-peaking technique has been introduced so as to enhance the bandwidth by utilizing the resonance characteristics of LC networks. In addition to this arrangement, a new negative differential current feedback technique has been put forward for the discussion so as to boost the bandwidth of the system and to reduce the value of peaking inductors.
This pre-amplifier circuit has been implemented in TSMC 0.
For an optical front-end with a 0. The vast distances of optical fiber span the globe, connecting the world together in an intricate communications infrastructure. With the drive towards portable and multimedia communications, the system has increasingly faced with the challenge of bringing the capacity of our communications infrastructure directly to the user, providing seamless access to vast quantities of information, any where and anytime.
Whether it is the transfer of an image from a digital camera to a laptop computer or the communication of data within a massively parallel computer, there is an urgent need to develop new methods of high speed data communications. Light offers many advantages as a medium for communication. Whether travelling through free space or through optical fiber, light enjoys unequalled channel bandwidth, and is capable of data rates in the terabits per second.
This immense capacity is due to the nature of the photons that constitute an optical signal. As such, the optical signals neither generate nor are sensitive to electromagnetic interference EMI , parasitic coupling, and other problems faced by electrical.
Given their advantages, optical links are rapidly expanding into application areas beyond traditional fiber-optic links. The success of such short-range systems is particularly telling of how optical communication systems are likely to proliferate in the future: as of , over million laptops, digital cameras, and other devices were shipped equipped with IrDA-compatible serial ports, and currently over 40 million new devices are being produced yearly.
Figure 1. On the transmit side, an information source produces a data stream that is encoded and sent to the appropriate drive circuitry used to modulate the optical signal generated by either a light emitting diode LED or laser. The signal propagates through free space or through a waveguide such as optical fiber until it reaches the photo detector on the receiver end. The photo detector converts the optical signal into an electric current that is sensed by the optical pre-amplifier and regenerated to a sufficiently strong voltage signal from which the original data can be recovered by the demodulator.
The expansion of optical communications into new applications has created exciting opportunities for the research and innovation of optical receivers. While the growth of fiber- optic networks in the last few decades has refined our understanding of optical receivers, its primary focus has been on speed and sensitivity. With the expansion of optical communications come new requirements on receiver designs. Probably the most widespread trend has been that of increased system integration and the drive to reduce system components, cost, and size.
Traditionally, optical receivers have not been subject to many system level constraints since optical receivers for long-haul fiber-optic networks are principally designed for performance rather than cost. As such, they have typically used advanced high-speed semiconductor technologies such as GaAs and Si bipolar processes.
Increasingly, the new optical receiver designs are being implemented in low-cost, high- integration technologies such as CMOS. One of the dominant trends is the continuous reduction of the system supply voltage as shown in Figure 1.
Increasingly, the supply voltage is seen as an adaptable design parameter used to optimize performance and minimize power. The logic circuits that operate with supply voltages near or even below the threshold voltage are being reported alongside analog circuits that do the same. The low-voltage operation is partly driven by the desire for low power in portable applications and in applications that require battery back-up such as fiber-to-the-home FTTH.
In the end, low-voltage operation will be crucial to the long-term viability of integrated optical receivers . Figure 2 Projected trends in system supply voltages. The recent advance in CMOS technology, mainly driven by the low-power applications, has significantly lowered supply voltage.
As a result, the performance of voltage mode circuits, such as dynamic range, is affected greatly. CMOS current-mode circuits offer many attractive advantages over their voltage-mode counterparts. The key performance feature of current- mode circuits is their inherent wide bandwidth.
The other advantages include low supply voltage requirement, large dynamic range, and tunable input impedance. These characteristics make current-mode circuits particularly attractive for high-speed interface circuitry. The analog amplifiers are susceptible to power and ground fluctuations caused by the switching of digital portion of mixed-signal circuits, such as clock and data recovery circuits in optical transceivers.
The accuracy of current-mode circuits is severely affected by the errors due to device mismatches. Low-voltage current-mode circuits that are insensitive to device mismatches and switching noise are highly desirable. In addition, a main drawback of current- mode circuits is their low current gain. To increase the current gain, the size of the transistor in the output branch can be made large, how-ever, at the cost of reduced bandwidth.
The technique introduced increases the bandwidth of current-mirror amplifiers by cancelling out the dominant pole with a compensating zero obtained by inserting a resistor between the gates of the input and output transistors of the amplifiers. In this system, an adjustable gain optical amplifier is used in front of the photo receiver, so as to reduce both the requirement in receiver sensitivity and the amount of gain required from the electronic amplifier.
A flip-flop is then used so as to perform the decision making part. The signal transmission over the fiber suffers from a number of impairments such as chromatic dispersion enhanced by the chirp characteristics of the source, polarization mode dispersion, nonlinear channel interaction. Such impairments are getting more and more detrimental as the bit rate increases, most often they can be compensated at the optical signal power level or electronically at the receiver level .
The detailed schematic of the transmitter and receiver has been shown in figures 3 and 4 respectively.
For the analog parts, what matters first is the gain available over the required bandwidth from a given technology; much attention is then paid to the power gain cut-off frequency FMAX, known as the maximum oscillation frequency i. Figure 5 Gain vs. These four parameters can be traded off against each other. By adjusting the number of amplifying stages, the transistor sizes, and the bias voltages, the receiver circuit can be designed to optimize the link performance i.
The rise times for the receiver components are given in Table I. This is achieved with an appropriate value feedback resistor.