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 : Non- Inverting Amplifiers – Part 2 – Derivations Prepared by: Ing. Jaroslav Bernkopf.

missy
Télécharger la présentation

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: Non-InvertingAmplifiers – Part 2 – Derivations 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. Voltage Gain Let‘s apply a voltage V1 of +1 V to the input of the amplifier in the figure. Thevoltagedifferencebetweentheinputs V+ and V- iszero. Thisimpliesthatthevoltage on the input V- isthesame as the input voltage, i.e. +1 V. This voltage will cause a current to flow through the resistor R1. What will this current be? V+ V1 = +1 V V- +1 V Operational Amplifiers

  3. Voltage Gain The voltage across the resistor R1 is 1 V. Using the Ohm‘s law we can calculate the current through the resistor R1: V+ V1 = +1 V V- +1 V VR1 = 1 V IR1 = 1 mA Operational Amplifiers

  4. Voltage Gain • Can thiscurrentflow fromthe input V-? • No, it can‘t, because as we know • the input resistance of an op amp is infinite • the input current of an op amp is zero • So the current ofthe resistor R1 has to flowthroughR2. V+ V1 = +1 V V- IR2 = 1 mA +1 V VR1 = 1 V IR1 = 1 mA Operational Amplifiers

  5. Voltage Gain The current of 1 mA will create a voltage drop across the resistor R2. We can calculate it using the Ohm‘s law: VR2 = IR2 * R2 VR2 = 1mA * 10k VR2 = 10 V V+ V1 = +1 V VR2 = 10 V V- IR2 = 1 mA +1 V VR1 = 1 V IR1 = 1 mA Operational Amplifiers

  6. Voltage Gain What is the value and thepolarity of the output voltage? Theupper end of R1 is positive withrespect to theground. We can draw a small plus sign to theupperendof R1, a minus sign to itslowerend. Thecurrentthrough R2 isthesame as thecurrentthrough R1: Itflowsfromabove to below. Wecandrawthesame plus and minus signs to theendsof R2. V+ V1 = +1 V + VR2 = 10 V V- IR2 = 1 mA - +1 V + VR1 = 1 V - IR1 = 1 mA Operational Amplifiers

  7. Voltage Gain The output voltageconsistsof the sum of twoindividual resistor voltage drops. These voltage drops are in series, liketwobatteries. Theirvoltagesaddtogether. Thetotal output voltage V2 is V2 = VR1 +VR2 V2 = 1 V + 10 V V2 = 11 V The output voltageis positive and itsvalueis +11 V. V+ V1 = +1 V + VR2 = 10 V V- IR2 = 1 mA - +1 V V2 = +11 V + VR1 = 1 V - IR1 = 1 mA Operational Amplifiers

  8. Voltage Gain • What is the voltage gain? • As youcan see, the amplifier makes • elevenvolts out of one volt • positive output voltage out of positive input voltage • Its voltage gain must be +11. V+ V1 = +1 V + VR2 = 10 V V- IR2 = 1 mA - +1 V V2 = +11 V + VR1 = 1 V - IR1 = 1 mA Operational Amplifiers

  9. Voltage Gain Look at the voltages and at the values of the resistors: Do the values look so similar just by accident? No, it is no accident. V+ V1 = +1 V + VR2 = 10 V V- IR2 = 1 mA - +1 V V2 = +11 V + VR1 = 1 V - IR1 = 1 mA Operational Amplifiers

  10. Voltage Gain The voltage gain is determined by the voltages: The voltages are determined by the values of the resistors. Therefore, the voltage gain is determined by the resistors: V+ V1 = +1 V + VR2 = 10 V V- IR2 = 1 mA - +1 V V2 = +11 V + VR1 = 1 V - IR1 = 1 mA Operational Amplifiers

  11. Voltage Gain This is the equation we are looking for: Now you can forget it. Because in future you will always be able to derive it again. V+ V1 = +1 V + VR2 = 10 V V- IR2 = 1 mA - +1 V V2 = +11 V + VR1 = 1 V - IR1 = 1 mA Operational Amplifiers

  12. Task • Construct the first stage of a preamplifier for record players. • The preamplifier should have the following features: • Input resistance Rin = 47kΩ • Voltage gain Av = 34 • Use the conception shown in the figure below. V+ V- Operational Amplifiers

  13. Solution The input resistance Rinof anon-inverting amplifier is infinite. Thedesired input resistanceRinof thepreamplifieris 47 kΩ. Ri = ∞ V+ V- Rin = ∞ Operational Amplifiers

  14. Solution Wemustaddanotherresistor R3 = 47k in parallel to achievethe desired input resistance Rin= 47kΩ. V+ V- Rin = 47k Operational Amplifiers

  15. Solution Thevaluesof R1 and R2 are not given. Let‘schoosetheresistanceof R1 = 1kΩ. Thenwewillcalculatethevalueof R2. V+ V- 1k Operational Amplifiers

  16. Solution The equationforthevoltage gain is: 1 Let‘s express R2: Let‘s substitute theknownvaluesforAv and R1: V+ 33k 1k V- Rin = 47k Theresistanceof R2 willbe33 kΩ. 1k Operational Amplifiers

  17. References • http://www.wikipedia.com • http://www.thefreedictionary.com Operational Amplifiers

More Related