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Published in Chunlei Guo, Subhash Chandra Singh, Handbook of Laser Technology and Applications, 2021
In ‘conventional’ electronics, whereby the word ‘conventional’ for the present purposes, we mean frequencies where solid-state devices such as transistors or diodes will operate, say below 1011 Hz, an oscillator is conveniently constructed by applying an appropriate amount of positive feedback to an amplifier. Such an arrangement is shown schematically in Figure 2.1. The input and output voltages of the amplifier are Vi and Vo, respectively. The voltage gain of the amplifier is A0 where, in the absence of feedback, A0 = Vo/Vi. The feedback circuit returns part of the amplifier output to the input. The feedback factor β=|β|ejϕ is, in general, a complex number with amplitude |β| ≤ 1 and phase ϕ.
Electronic Circuits
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
An oscillator has an amplifying device, a feedback network, frequency-determining components, and a dc power source. The amplifier is used primarily to increase the output signal to a usable level. Any device that has signal gain capabilities can be used for this function. The feedback network can be inductive, capacitive, or resistive. It is responsible for returning a portion of the amplifier’s output back to the input. The feedback signal must be of the correct phase and value in order to cause oscillations to occur. In-phase, or regenerative, feedback is essential in an oscillator. An inductor-capacitor (LC) network determines the frequency of the oscillator. The charge and discharge action of this network establishes the oscillating voltage. This signal is then applied to the input of the amplifier. In a sense, the LC network is energized by the feedback signal. This energy is needed to overcome the internal resistance of the LC network. With suitable feedback, a continuous ac signal can be generated. The output of a good oscillator must be uniform and should not vary in frequency of amplitude.
Devices in Optical Network Node
Published in Partha Pratim Sahu, Fundamentals of Optical Networks and Components, 2020
Gain is a ratio of the output power of a signal to its input power. The performance of amplifiers are represented by gain efficiency as a function of pump power in dB/mW, where pump power is the energy required for amplification. The gain bandwidth of an amplifier defines as a range of frequencies or wavelengths over which the amplifier amplifies effectively. In a network, the gain bandwidth provides the number of wavelength channels obtained for a given channel spacing. The gain saturation point of an amplifier states that when the input power is increased beyond a certain value, the carriers (electrons) in the amplifier are unable to output any additional light energy. The saturation power is typically defined as the output power at which there is a 3-dB reduction in the ratio of output power to input power. Polarization sensitivity refers to the dependence of the gain on the polarization of the signal. The sensitivity is measured in dB and refers to the gain difference between the TE and TM polarizations.
A novel design procedure of a compact-size X-band shunt feedback amplifier
Published in International Journal of Electronics, 2023
Hafiz Hejazi, Majid Baghaei Nejad
High-frequency amplifiers are the most important components of every communication system. In most high-frequency systems, three types of amplifiers are used: low noise amplifiers (LNAs), inter-stage amplifiers (ISAs), and power amplifiers (PAs) (Razavi & Behzad, 2012). Depending on the system specification, these amplifiers may be situated near the input, output, or wherever in between the RX/TX channels. Inter-stage amplifiers cannot be designed using the same topologies as PAs and LNAs. In PA design, due to the stabilisation network of such amplifiers, NF is very high. Furthermore, they are power-hungry blocks whose properties can be easily altered throughout the fabrication process (A. De Hek et al., 2005; Alizadeh & Medi, 2016; Alizadeh et al., 2016; Nikandish et al., 2014; Pajic et al., 2005). On the other hand, standard LNA structures are not suitable for the aforementioned purpose in terms of output power (Hu & Ma, 2019; Nikandish & Medi, 2014; Nikandish et al., 2016).
MOS Amplifier Design Methodology for Optimum Performance
Published in IETE Journal of Research, 2020
Abir J. Mondal, Paromita Bhattacharjee, Pinaki Chakraborty, Bidyut K. Bhattacharyya
Basically, an amplifier controls its output signal to make it stronger than the input signal as a measure to avoid violation of the operation of proceeding stages of the circuit. For example, an indispensable block of an analog system is the single-stage amplifier. Differential amplifiers are cascaded with them to form an operational amplifier (op-amp). However, single-stage amplifier acts as a buffer for impedance matching while connected at the output of an op-amp. Cascode amplifiers in particular yield a close to ideal current source since it has very high output impedance. They are widely used to bias transistors and devices to be matched while realizing an op-amp. Every analog circuit has output performance measurements which determine its behavior. Different parameters such as dc gain, Av, GBWP/UGF product, slew rate, SR, and power dissipation govern the performance of a cascode amplifier. Design of such an amplifier becomes complex, as these parameters involve interdependent trade-offs. Also, inherent device noise and environmental noise have a huge impact on the working of a circuit. In view of that improvement and expansion in the field of design optimization, automation and verification of analog circuits are exceedingly sought after. Furthermore, a variation in system performance detail solicits a generalized design procedure in order to address the design specification.
Experimental investigation on a flapping beam with smart material actuation for underwater application
Published in Mechanics of Advanced Materials and Structures, 2021
Ganesh Govindarajan, R. Sharma
Arrangements for the calibration of displacement of the beam are shown in Figure 4. The dimensions of the active part of MFC actuators are 103 × 57 × 60 mm. The beam is excited using the MFC and it is connected to an amplifier and the frequency is varied, while the strain gauge measured the response of beam and stored it on PC. The thrust is measured using the strain gauge, where the relationship between voltage and force from the strain gauge reading is linear [14]. The function of voltage amplifier which amplifies the input voltage and the gain is the relationship that exists between the two signals, that is, one measured at the output and the other measured at the input.