China
Africa
Explore chapters and articles related to this topic
High-Performance Analog Circuits
Published in Wai-Kai Chen, Analog and VLSI Circuits, 2018
Chris Toumazou, Alison Payne, John Lidgey, Alicja Konczakowska, Bogdan M. Wilamowski
The current-feedback operational amplifier has two major advantages, compared to its voltage-feedback counterpart. First, the closed-loop bandwidth of the current-feedback amplifier is larger than that of classical voltage-feedback design for comparable open-loop voltage gain. Second, the currentfeedback operational amplifier is able to provide a constant closed-loop bandwidth for closed-loop voltage gains up to about 10. A further advantage of the current-feedback architecture is an almost unlimited slew rate due to the class-AB input drive, which does not limit the amount of current available to charge up the compensation capacitor as is the case in the conventional voltage-feedback op-amp. This high-speed performance of the current-feedback operational amplifier is extremely useful for analog signal-processing applications within video and telecommunication systems.
A new low voltage low power fully differential CMOS class AB current output stage with unique current drive capability
Published in International Journal of Electronics, 2023
Behnam Abdoli, Seyed Javad Azhari
The Current Operational Amplifier (COA) is one of the most important building blocks of the current-mode circuits/systems/tasks as both biomedical and portable applications, filter design, and many analog/digital/mixed signal processing (Altun & Kuntman, 2006; Behesht Ara & Azhari, 2015; S. Pennisi et al., 2006). One of the main parts of the COA is Undoubtedly the current output stage (COS) which plays a key role in the performance of the whole COA and determines some of the main parameters such as linearity, output impedance and most decisively the value and drive capability of the output current (Papazoglou & Karybakas, 1998; Safari & Azhari, 2011). These two measures are so vital that if are not sufficiently high, the outcomes of even best-performed preceding stages of the COA become of no use. The COS is also a main part of other current-mode amplifiers like CFOA (current feedback operational amplifier) and transconductance amplifiers. Thus, with a large range of applications, it has attracted a world widely attention (Arbel & Goldminz, 1992; Centurelli et al., 2007; G. Pennisi et al., 1995; Kashtiban & Azhari, 2009; Palmisano & Pennisi, 2000a; Palmisano & Pennisi, 2000b Palmisano et al., 1998, 2000; Palumbo & Pennisi, 1999; S. Pennisi, 2002; Youssef & Soliman, 2005; Zeki & Kuntman, 2000).
On the Effect of Operational Amplifier Gain-bandwidth Product on the Performance of Basic Building Blocks
Published in IETE Journal of Education, 2022
In this paper, we have reviewed several circuits using the finite gain-bandwidth product of the opamp. The students shall be taught about these to realize the importance of taking into account the non-idealities of the opamp in the design process. These ideas are applicable for circuits using other active devices, such as operational transconductance amplifiers and current mode devices such as a current conveyor (CC) and a current feedback operational amplifier (CFOA). Note that these devices have non-idealities such as finite input resistance, output resistance, output capacitance, current and voltage transfer gains, and internal poles. In this paper, we have not considered other non-idealities of the opamp viz., offset voltage and noise that affect the realizable dynamic range. Furthermore, a similar analysis needs to be carried out for high-order filters using several opamps by considering non-idealities of all opamps for realizing the desired performance.
CMOS voltage and current feedback opamps: a comparison between two similar topologies
Published in International Journal of Electronics Letters, 2021
Hervé Barthélemy, Valentin Gies, Stéphane Meillère, Rémy Vauché, Edith Kussener, Manon Fourniol
These implementations are discussed in section 2. In section 2.1, an overview of the ideal operational transconductance conveyor (OTC) (Barthélemy et al., 2018) and of the ideal operational transconductance amplifier (OTA) (Senani, 2014; Thanki, Sanghani, & Lamba, 2011) is given. In section 2.2, the OTA and the OTC are used to describe the voltage feedback operational amplifier (VFOA) and the current feedback operational amplifier (CFOA) respectively (Instruments, 2008; Senani, Bhaskar, Singh, & Singh, 2013). In section 3, the two CMOS architectures with similar sizes are analysed theoretically and simulated from LTSPICE (Antognetti and Massobrio, 1990, Analog Device) using the typical CMOS 0.35 μm BSIM3V3 transistor models from AMS (Multi-Project Circuits). In most applications opamps operate at frequencies below 1 GHz, a 0.35 μm provides a high performance/power ration for operation at these frequencies (Tunheim, 2002). Moving in Higher frequency, it could be more advantageous to use 0.18 μm or below especially if the analog must live in the same chip with a high-density digital part (Tunheim, 2002). However, due to the channel modulation effect, it is often necessary to size the transistors lengths higher than their minimal value; because this allows to provide high transistor output resistances, even if a cascode technique is used. Finally, a conclusion is given in section 4.