Tham khảo tài liệu 'new approaches in automation and robotics part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Operational Amplifiers and Active Filters A Bond Graph Approach 293 6. Feedback operational amplifier An op-amp that uses feedback is called a feedback is called a feedback amplifier. A feedback amplifier is sometimes referred to as a closed loop amplifier because the feedback forms a closed loop between the input and the output. A feedback amplifier essentially consists of two parts an op-amp and a feedback circuit. The feedback circuit can take any form whatsoever depending on the intended application of the amplifier. This means that the feedback circuit may be made up of either passive components active components or combinations of both Gayakward 2000 . A closed loop amplifier can be represented by using two blocks one for an op-amp and another for a feedback circuit. There are four ways to connect theses two blocks. These connections are classified according to whether the voltage or current is fed back to the input in series or in parallel as follows 1 Voltage series feedback 2 Voltage shunt feedback 3 Current series feedback and 4 Current shunt feedback Gayakward 2000 and Floyd Buchla 1999 . The voltage series feedback configuration is one of the most important because this is commonly used. An in depth analysis of this configuration in the physical domain is presented in this section computing voltage gain input resistance output resistance and the bandwidth. A bond graph model of a noninverting amplifier An op-amp connected in a closed loop configuration as a noninverting amplifier is shown in Fig. 11. The input signal is applied to the noninverting input. A portion of the output is applied back to the inverting input through the feedback network in the physical domain. The BGI and the Bond Graph in a Derivative causality assignment BGD are shown in Fig. 11 in order to get the symbolic expressions of the closed loop system in steady state applying the methodology given in section 1. Fig. 11. Bond graph models of a noninverting amplifier. The closed .
