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Signal Conditioning and Output Devices
Published in Francis S. Tse, Ivan E. Morse, Measurement and Instrumentation in Engineering, 2018
The open-loop gain-frequency characteristics of an op-amp are illustrated in Fig. 6-3b (solid line). The dc gain A is of the order of 106. The gain is down by 3 dB at about 10 Hz. An op-amp can be compensated in ternally to approximate a 6-dB/octave roll-off [20 dB/decade or a–1 slope in a log-log plot (see Sec. 4-6)]; that is, the open-loop gain A decrases with increasing operating frequency. The open-loop gain-bandwidth productis about 1 MHz, as shown in the figure. A constant gain-bandwidth product means that the gain is the reciprocal of frequency. Knowing this, the gain-bandwidth product for closed-loop operations can be predicted. For example, if the closed-loop gain is 103 (dashed line), the corresponding bandwidth is from dc to 1 kHz.
Operational amplifiers
Published in John Bird, Electrical and Electronic Principles and Technology, 2017
The open-loop voltage gain of an op amp is not constant at all frequencies; because of capacitive effects it falls at high frequencies. Fig. 21.3 shows the gain/bandwidth characteristic of a 741 op amp. At frequencies below 10 Hz the gain is constant, but at higher frequencies the gain falls at a constant rate of 6 dB/octave (equivalent to a rate of 20 dB per decade) to 0 dB. The gain-bandwidth product for any amplifier is the linear voltage gain multiplied by the bandwidth at that gain. The value of frequency at which the open-loop gain has fallen to unity is called the transition frequency fTfT=closed-loop voltage gain×bandwidth In Fig. 21.3, fT = 106 Hz or 1 MHz; a gain of 20 dB (i.e. 20 log10 10) gives a 100 kHz bandwidth, whilst a gain of 80 dB (i.e. 20 log10 104) restricts the bandwidth to 100 Hz.
Electronic circuit applications
Published in Joe Cieszynski, David Fox, Electronics for Service Engineers, 2012
The gain of an amplifier and its bandwidth are related and there is always a gain/bandwidth product so that increasing the amount of negative feedback reduces the gain but increases the bandwidth. The circuit designer therefore has the opportunity to produce with accuracy the amplifier desired. Figure 12.18 shows the circuit symbol and pin lead out connections for a 741 IC, along with a simple circuit arrangement.
An Assessment of Progress in 5.8 GHz Quasi-lumped Element Resonator Antennas
Published in IETE Technical Review, 2021
Shahanawaz Kamal, Abdullahi S. B. Mohammed, Mohd Fadzil Bin Ain, Fathul Najmi, Roslina Hussin, Zainal Arifin Ahmad, Ubaid Ullah, Mohamadariff Othman, Mohd Fariz Ab Rahman
Preliminary, considering the definition of quasi-LE which states that their extents are much minute than the wavelength; the mutual coupling effects experienced between closely placed radiating components are more minor in contrast to the distributed elements [133–139]. The compact dimensions also enable smaller amplitude or phase variations. At microwave frequencies, high-impedance lines possessing inductive characteristics along with associated shunt capacitance are typically employed. This ultimately compromises the gain-bandwidth product of the circuit. Engagement of lumped inductors with much lower parasitic capacitance outcomes in to a broader bandwidth. All of these factors can ultimately reduce the costs drastically.