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Circuits: Op Amps Page

The Op Amp Page

Here is 'everything you need to know' about op amps. Why do we love them so much?

1) We can build a huge variety of extremely useful circuits Links to an external site. with them including amplifiers, buffers, inverters, etc.

2) We can use them to isolate input and output circuits. Since the current going in to the op amp =0, the input circuit can be set up so it does not have to 'source' any current (often it can't or shouldn't).  The current for the output circuit comes from the POWER SUPPLY for the op amp, rather than from the input circuit.  The voltage follower/buffer below works on this principle.

Lectures:

Lecture (4-1) Op-Amp Characteristics

Lecture (4-2) Negative Feedback

Lecture (4-3) Ideal Op-Amp Model and Non-Inverting Amplifier

Lecture (4-4) Inverting Amplifier

Lecture (4-5) Summing Amplifier

Lecture (4-6) Difference Amplifier

Lecture (4-7) Voltage Follower

Cookbooks (quick-notes):

Download Op Amp Cookbook.docx

Download Op Amp Cookbook -- Recognizing Inv & NonInv Amps.docx

Download Op Amp Cookbook -- Recognizing Inv & NonInv Amps ANSWERS.docx

What you need to know about an ideal op amp:

a) with feedback:  Vp=Vn and input currents =0. 

b) without feedback Vo = A(vp-vn) where A is so large that Vo 'rails' between +Vcc and -Vcc (op amp used as switch below, uses that principle)

c) for all cases -Vcc < Vo < Vcc (op amp 'rails out' at (cannot go above or below) power supply voltages)

Quick Video Summaries of common op amp circuits:

Download (Power Point to take notes on)

Op Amp as Switch:

http://www.youtube.com/watch?v=i1Ol7JpH-Sw Links to an external site.

Non-Inverting Amplifier:

http://www.youtube.com/watch?v=CfORgEU-hFM Links to an external site.

Inverting Amplifier:

http://www.youtube.com/watch?v=vjIxw6I1NF8 Links to an external site.Non-Inverting Summer (adder):

http://www.youtube.com/watch?v=u8RjjRIC8hY Links to an external site.

Inverting Summer (adder):

http://www.youtube.com/watch?v=cTN-w6_HzgI Links to an external site.

Differencing (subtracting) amplifier:

http://www.youtube.com/watch?v=O8nSDOG9MDo Links to an external site.

Voltage Follower:

http://www.youtube.com/watch?v=ScNFmIPZQxQ Links to an external site.

Designing Op Amp Circuits:

Here is the original deck of cards I used in class: Download deck of cards print.pptx

You might find this one even easier to use (block diagrams shown via math symbols) Download deck of cards op amps version B.pptx

Labs:

Lab 4 -- Resistive Sensors  (using the op amp as a switch, and also (extra credit) an inverting amplifier)

Lab 5 -- Op Amp D/A Converter (using the op amp as non-inverting amplifier)  See also Download OpAmp DtoA conversion.pdf

Intro to Op Amps, How they Work, and how the pins are laid out

http://www.youtube.com/watch?v=5my9_kRYVqc&list=PL170A01159D42313D&index=11&feature=plpp_video

Examples:  Review For Midterm Ii

Identifying common op amp circuits:

Download Op Amp Cookbook -- Recognizing Inv & NonInv Amps.docx

Download Op Amp Cookbook -- Recognizing Inv & NonInv Amps ANSWERS.docx

Analysis of op amp circuits:

Download OpAmp (diff amp) Node Voltage Example.pdf

Download OpAmp (inv amp) Thevenin example.pdf

Download OpAmp (resistance bridge) Thevenin Example.pdf

Design examples (common op amp circuits):

Download OpAmp Design examples (amp & summer).pdf

Design examples (cascaded op amps):

Download OpAmp Linear Algebraic example 1.pdf

Download OpAmp Linear Algebraic example 2.pdf

Download OpAmp Linear Algebraic example 3.pdf

Download OpAmp Linear Algebraic example 4.pdf