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Guarding and Shielding
Published in Anton F. P. van Putten, Electronic Measurement Systems, 2019
If we consider the different types of active element then a single-input amplifier such as a transistor, with a single-ended output, is a device which cannot be considered as an ideal active element. An ideal active element can be defined as a controllable power source with no limitations in polarity, in voltage and current at both the input and the output. A good example of such an active element is the operational amplifier which is called a nullor in its most ideal form. In a nullor, the input current, ii, and the input voltage, vi, by definition are claimed to be zero.
Mathematical modelling of semiconductor devices and circuits
Published in Rajesh Singh, Anita Gehlot, Intelligent Circuits and Systems, 2021
Sanjay Kumar Roy, Manwinder Singh, Kamal Kumar Sharma, Brahmadeo Prasad Singh
The nullor is an active two-port network consisting of nullator and norator. The circuit symbol of the nullor in the most basic form is depicted in Figure 14.2. Thus, the nullator is connected as the input port of the nullor whereas the norator forms its output port.
Synthesis of Some Specific Types of Voltage/Current Transfer Functions with Minimum Number of Passive Elements and One Active Device
Published in IETE Journal of Research, 2023
Numerous first-order voltage transfer functions (VTF) and current transfer functions (CTF) all-pass filters with passive elements [1,2], employing different types of active elements, such as operational amplifier (OA) [3–5], various types of current conveyors (CC) [6–20], operational trans-resistance amplifier (OTRA) [5,21–24], four terminal floating nullor (FTFN) [25–29], current operational amplifier (COA) or current feedback amplifier (CFA) [30,31], differential voltage current conveyor (DVCC) [9,32–36], current differencing trans-conductance amplifier (CDTA) [35,36], current differencing buffered amplifier (CDBA) [37] are available in the literature. These circuits enjoy some of the feature(s) of grounded components, minimum number of passive components, single active element, low-input and high-output impedances.
On the Effect of Operational Amplifier Gain-bandwidth Product on the Performance of Basic Building Blocks
Published in IETE Journal of Education, 2022
The opamp can be modeled in several ways. The routine hand analysis of circuits usually uses the opamp finite gain model (2), and the student should only know how to write using Kirchoff’s current law (KCL), the equations at each node and then the circuits can be analyzed using matrix methods or solutions by hand for deriving the transfer function, input and output impedances. Circuit analysis programs like SPICE, however, based on a description of the circuit – how components are connected between various nodes – use the modified nodal analysis to derive the frequency response, analyze noise, etc. On the other hand, another way of analyzing analog circuits in a computer-aided manner is known as Symbolic analysis. In this technique [10,11], the active devices such as opamp, Current Conveyor (CC), Operational Transconductance Amplifier (OTA), etc. are modeled using pathological elementsviz., nullor (comprising of a nullator and a norator), Voltage mirror – Current mirror (VM-CM) pairs. The equations describing the complete circuits can be derived using standard nodal analysis and analyzed using matrix methods. The transfer functions etc., can be derived in terms of various parameters in the circuit such as resistors and capacitors, as symbolic expressions. In this paper, we use the model of (2) and use only simple circuit analysis techniques.
New Electronically Tunable Low-frequency Quadrature Oscillator Using Operational Transresistance Amplifier
Published in IETE Journal of Research, 2022
Gurumurthy Komanapalli, Rajeshwari Pandey, Neeta Pandey
Our Literature study suggests there are few low-frequency sinusoidal oscillators (LFSOs) available [1–11,16] despite its wide application. Among these topologies, only [11,16] qualifies for generating low-frequency quadrature sinusoid waveforms. Whereas, [1–10] delivers single-phase outputs. Reference [11] presents a QO based on the current differencing buffered amplifier (CDBA). Sinusoidal oscillators discussed in [8–10,16] entail OTRA [17–19] as an active component. Whereas [1–2] and [3–6] presents an operational amplifier (Op-amp) and current feedback amplifier (CFOA) based LFSOs. The oscillator presented in [7] uses mixed ABBs, i.e. a combination of positive four terminals floating nullor (pFTFN) and operational Transconductance amplifier (OTA).