Operational Amplifiers - Comparators

How operational amplifiers (op amps) can be used to compare two input voltages to determine which one is higher. Op amp Schmitt triggers, which are comparator circuits with some hysteresis, are also covered.

Presented by David Williams ( http://www.elen.ca ) from the Electronic Engineering Technology department at Okanagan College ( http://www.okanagan.bc.ca/electronics )

Category:

Education

Tags:

• electronic circuits
• operational amplifiers
• op amps
• comparators
• Schmitt triggers

[tarbidian]

Why is it 20k and not 15k?

4k/2k = 20k/10k

[tarbidian]

OKSemi, you are correct, the LDR needs to be 20k not 15k. Thanks for pointing that out...time for some annotations.

[goodmorningimage]

great video. im working on my final year project and il be sure to view your other videos. it was a great help and you presented it prefectly

[josepep]

thank you for the video!!!!!!!!!!!!!!!!!!!

[URKIDN1]

this is awesome :) good tut

[cepedin]

hi, i think you are wrong in your last ecuation cause r1=13.45 / r2= 0.05 = 269.

[OKSemiconductor]

(@ t = 7:50) Hey David,

I don't know if I'm missing something, but as far as I can tell a value of 15k for the photocell won't make the light turn on:

12V * (15k / (15k + 10k)) = 7.2V

Should it be?

12V * (20k / (20k + 10k) = 8V

Am I missing something?