CHAPTER 8 IDEAL OPERATIONAL AMPLIFIER AND OP-AMP CIRCUITS inverting output non-inverting Op-amp circuit symbol • Open loop mode • Vo = Aod ( V2 – V1) – Aod is referred to as the open loop gain. – Notice that is V2 = V1, the open loop gain equals to Final Exam SEM II 2012/2013 An ideal op-amp, was measured in a lab experiment in open-loop mode. Determine the open loop gain (Aod) and complete the table below which shows the results of the experiment. V1 (1) -1mV -0.5V 0.99 V V2 (2) +1mV -0.506 V 1V Vo (3) 1V -3V 5V • Op amp can be configured to be used for different type of circuit applications: – Inverting Amplifier – Non – inverting Amplifier – Summing Amplifier – Integrator – Differentiator Inverting Amplifier Op-amp as an inverting amplifier Voltage at node 1 (inverting) = voltage at node 2 (non-inverting ) KCL at node 1: (Vi – 0) / R1 = (0 – Vo) / R2 Vi / R1 = - Vo / R2 Vo = - R2 Vi R1 Exercise 8.3 Gain = - (R2 / R1) = -(150/12) = -12.5 Can the voltage gain be calculated the using the same formula? Try and use the same method in deriving Vo/Vi Non - Inverting Amplifier Voltage at node 1 (inverting) = voltage at node 2 (non-inverting ) KCL at node 1: (0– Vi) / R1 = (Vi – Vo) / R2 -(Vi / R1) = (Vi / R2) – (Vo / R2) Vo / R2 = (Vi / R2) + (Vi / R1) = Vi 1 + 1 R2 Vo / Vi = R2 1 + 1 R2 R1 R1 Noninverting amplifier Voltage Follower / Buffer Amplifier Vo = Vi Hence, gain = 1 Summing Amplifier Summing Similarly,Amplifier i1 + i2 + i3 – i4 – 0 = 0 Output voltage Solution: output voltage Other Op-Amp Applications Integrator Integrator circuit Differentiator EXAMPLE 8.4 Differentiator circuit Calculating Gain and Design Questions NON - INVERTING INVERTING Calculating Output and Design Questions SUMMING AMPLIFIER INTEGRATOR AMPLIFIER DIFFERENTIATOR AMPLIFIER Calculate the input voltage if the final output, VO is 10.08 V. What is the value of Vin1 from the figure above? Calculate the output voltage, VO if V1 = V2 = 700 mV IDQ Answering the questions • Please write down the questions you attempted on the cover page • Organize your thoughts. When it is organized, so will your workflow. – Messy work will make the lecturers feel annoyed as they have to look for your answers – bear in mind that lecturer handling one section = 50-60 students – each paper has 5 questions – TOTAL – 250 to 300 questions to mark • Don’t leave a question blank – just write down anything you know that might be related • Be tactical. • Study smart, pray and tawakal.