The open-loop gain of the LF356, for instance, is flat at about $2 \times 10^5$ out to only 10Hz, and then decreases at 6dB per octave. This criterion is easy to meet at DC, but is problematic at higher frequencies because the open-loop gain decreases with frequency. So long as the closed-loop (with feedback) gain is substantially lower than the open-loop gain, say by $10^3$, the errors due to the finite gain will be unimportant. Īlthough an ideal op amp has an open-loop (no feedback) gain of infinity, all practical op amps have finite open-loop gains, typically around $10^5$ at DC. Resistor noise, also called Johnson, Nyquist, or thermal noise, results from the thermal fluctuations of the resistor’s electrons, and is proportional to the square root of the resistance, temperature and bandwidth. The resistors used in an op amp’s external circuit are also noisy. The input offset voltage, $V_\mathrm \, V = 1 \, \mu V \, (RMS)$. Consequently, the op amp's output is not precisely zero when $V_+=V_-$. The transistors and other circuitry in an op amp's differential input stage do not match perfectly. The most important imperfections can be divided into four categories: However, in certain circuits, op amps have imperfections which break the golden rules. The last two week’s exercises should have convinced you that op amps behave ideally in a wide range of useful circuits. How does the push-pull circuit in 8.11 work? What do you think is the origin of the name? Why does the capacitor in 8.3 mask 60Hz noise?ģ. Explain why it is necessary to divide by 1000 to obtain the input offset vol t age V os in 8. Perform any circuit calculations use MatLab or anything that can be done outside of lab RStudio (freeware).Īll parts spec sheets are located on the Physics 111 Library site.ġ.Answer the pre-lab questions utilizing the references and the write-up.This week’s lab explores some of these circuits, and investigates methods of curing some of the imperfections.īefore coming to class complete this list of tasks: However, some circuits expose op amp imperfections which violate the golden rules. In many circuits, op amps behave perfectly in the sense that the op amp golden rules are obeyed. NOTE: You can check out and keep the portable breadboards, VB-106 or VB-108, from the 111-Lab for yourself ( Only one each please) Reprints and other information can be found on the Physics 111 Library Site. The Art of Electronics, Horowitz & Hill Chapter 4, skim Chapters 2, 8.1 Microelectronics Circuits, Sedra & Smith Chapter 2, skim Chapters 4, 9, & 10Īrt of Electronics Student Manual, Hayes & Horowitz Chapter 4 © 2015 Copyright by the Regents of the University of California.
0 kommentar(er)
