1 / 17

Anglicky v odborných předmětech "Support of teaching technical subjects in English “

Anglicky v odborných předmětech "Support of teaching technical subjects in English “. Tutorial : Mechanic – electrician Topic : Electronics II. class Operational Amplifiers - Basics Prepared by: Ing. Jaroslav Bernkopf.

papina
Download Presentation

Anglicky v odborných předmětech "Support of teaching technical subjects in English “

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Anglicky v odborných předmětech"Support ofteachingtechnicalsubjects in English“ Tutorial: Mechanic– electrician Topic: Electronics II. class OperationalAmplifiers - Basics Prepared by: Ing. Jaroslav Bernkopf Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

  2. OperationalAmplifiers - Basics Definition: An operational amplifier(OA)is an integrated circuit that amplifies small voltage signals. It contains many transistors: 2

  3. OperationalAmplifiers - Basics • Description: • Anoperationalamplifier • has two inputs of opposite polarity • amplifiesonlythevoltagedifferencebetweenthetwoinputs • doesn‘tamplifytheparticularvoltages on theinputs • has a single output 3

  4. OperationalAmplifiers - Basics • Description: • Anoperationalamplifierhas • a very high voltagegainAv • a very high input resistanceRi • a very low input currentIi • a very low output resistanceRo 4

  5. OperationalAmplifiers - Basics We want the OAs to be as good as possible: We want them to be ideal. Real OAs are so good that usually we can assume our real OA to be ideal. 5

  6. OperationalAmplifiers - Basics If the voltage gain Av is infinite, then with the smallest possible voltage Vi between the inputs the output voltage Vo must be infinite too: Vi * Av = Vo 0.001 V * ∞ = ∞ V 0.0001 V * ∞ = ∞ V 0.00001 V * ∞ = ∞ V 0.000001 V * ∞ = ∞ V 0.0000001 V * ∞ = ∞ V and so on. But an infinite voltage on the output would be terribly dangerous, and unusable! Is it really infinite? No, it isn‘t. Why? 6

  7. OperationalAmplifiers - Basics Why isn‘t the output voltage infinite? There are two good reasons: An infinite voltage simply is not physicallypossible. The negative feedback works for us. We will explain thisin the following slides. 7

  8. OperationalAmplifiers - Basics Why can‘t the output voltage be infinite? Your OA can‘t give you more than it gets from you. And what does it get from you? It gets the supply voltage of let‘s say +15V and -15V. That‘swhyit can‘t give you more than +15V or less than -15V. The output voltage can‘texceed+15Vor -15V. 8

  9. OperationalAmplifiers - Basics Ifthereis a „reasonable“ voltage on theoutput, let‘s say 3 V like in thepicture, theonlypossibleexplanationis: ThevoltageVibetweentheinputsmustbezero! 9

  10. OperationalAmplifiers - Basics What forces the OA to behave so „reasonably“? The negative feedback always sets the output voltage to such a value that thevoltage between the inputs is zero. This knowledge will help us solve all OA-based circuits in this course. 10

  11. OperationalAmplifiers - Basics Example: There is a voltage +5.001 V on the V+ input, and +5.000 V on the V- input. The operational amplifier amplifies the differential voltage 0.001 V andignores the „common“ voltage 5 V. 11

  12. OperationalAmplifiers - Basics Question: What is the polarity of the output voltage? 12

  13. OperationalAmplifiers - Basics Answer: The output voltage is positive, because the V+ input is more positive than the other. 13

  14. OperationalAmplifiers - Basics Question: What is the output voltage? 14

  15. OperationalAmplifiers - Basics Answer: The voltage gain is infinite, there is no negative feedback. The OA tries to produce an infinite positive voltage on its output. But it can‘t produce more than +15V. The output voltage is close to +15V. 15

  16. OperationalAmplifiers - Basics Test: What can be true? Circle the correct answers! 16

  17. References http://www.wikipedia.com http://www.thefreedictionary.com Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013. Link: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro-konkurenceschopnost Technical Information - National Semiconductor LM741CN Datasheet

More Related