Need some help with Op-Amps

Thread Starter

happs

Joined Feb 27, 2005
24
Hey :)

Ok, I am still learning about electronics and have stumbled upon things called ... op amps. I got a 741 from radioshack and have no idea what it is for! I am teaching myself about electronics.

Does anyone know of a good tutorial about operational amplifiers ? I have pretty much looked at every single one that is brought up on Google.com and have read them through but with no sudden .. "ooooooooooooooooh! I seee" kinda response. So if anyoen knows of any simple to follow op amp tutorials then I would be very appreciative.

Also, if someone could please post some links to some very simple op-amp circuits ... ? Something simple like a light sensor circuit will be great. Am I correct in thinking that I should use an op amp when i want a light sensor (phototransistor) to turn on an LED instantly when it goes dim ? I have made the light sensor circuit and it works pretty well .. it's just a test circuit but using two transistors I have made a kind of amplifier to turn on an LED when it goes dark -- but this LED goes from off, to slightly on to on. I want it to just switch from off to on instantly -- is this what Operational amplifiers are for ?

Heheh ,, I know that I am asking quitea lot of questions but I woudl really like to find out about this part of electronics. I have made some other circuits using 4017's and 555 timers so I am not completely new, but this op amp stuff is really baffling me.

Any response wiill be great.
Thanks in advance.

- Happs
 

pebe

Joined Oct 11, 2004
626
Originally posted by happs@Feb 27 2005, 11:54 PM
Hey :)

Ok, I am still learning about electronics and have stumbled upon things called ... op amps. I got a 741 from radioshack and have no idea what it is for! I am teaching myself about electronics.

Does anyone know of a good tutorial about operational amplifiers ? I have pretty much looked at every single one that is brought up on Google.com and have read them through but with no sudden .. "ooooooooooooooooh! I seee" kinda response. So if anyoen knows of any simple to follow op amp tutorials then I would be very appreciative.

Also, if someone could please post some links to some very simple op-amp circuits ... ? Something simple like a light sensor circuit will be great. Am I correct in thinking that I should use an op amp when i want a light sensor (phototransistor) to turn on an LED instantly when it goes dim ? I have made the light sensor circuit and it works pretty well .. it's just a test circuit but using two transistors I have made a kind of amplifier to turn on an LED when it goes dark -- but this LED goes from off, to slightly on to on. I want it to just switch from off to on instantly -- is this what Operational amplifiers are for ?

Heheh ,, I know that I am asking quitea lot of questions but I woudl really like to find out about this part of electronics. I have made some other circuits using 4017's and 555 timers so I am not completely new, but this op amp stuff is really baffling me.

Any response wiill be great.
Thanks in advance.

- Happs
[post=5675]Quoted post[/post]​
There is a good tutorial on the website of this forum. Try this link:

http://www.allaboutcircuits.com/vol_3/chpt_8/1.html
 

spveer

Joined Feb 27, 2005
4
Hello...

Is an answer to this question possible?
Can anyone show me how this can be solved?

given 2 inverters and an infinite numbers of 2-input AND and OR gates.

Task is to get an output a', b', c', given inputs a, b, c.

inputs------>outputs
a------------->a’
b------------->b’
c------------->c’
(using 2 inverters and an infinite numbers of 2-input AND and OR gates)


I need the solution today pls

Pradeep
 

hgmjr

Joined Jan 28, 2005
9,029
Hi, Happs

You have picked a great place to post your question. The population of members to this website possess a very broad range of knowledge across the entire spectrum of electronics.

You have also picked a fun topic to explore. Opamps are one of the most useful devices available to the electronic circuit designer and hobbyist alike. Particularly if you are interested in exploring the analog circuit design world.

I see pebe and firestorm have provided some good website links to get you started.

Please don't hesitate to post any follow-up question as you make your way through the material that is available on this topic.

Good Luck
 

Firestorm

Joined Jan 24, 2005
353
well said hgmjr...the best way to learn is through asking questions...u dont truly understand something until u have asked "y"?
thx l8er

-fire
 

Nettron

Joined Jan 22, 2005
29
I have made a kind of amplifier to turn on an LED when it goes dark -- but this LED goes from off, to slightly on to on. I want it to just switch from off to on instantly -- is this what Operational amplifiers are for ?
Appears you are using the Opamp as a comparator (open loop), The "slightly on-to on" thingy happens 'cause the comparator needs some hysteresis, meaning you need to add some positive feedback from the output to the non-inverting input ( assuming you are using it for your reference voltage ).
 

Thread Starter

happs

Joined Feb 27, 2005
24
Hey peeps :)

Just wanted to say thankyou to everyone who helped me out with this. I have found some of those tutorials posted extremely useful and I now have a basic knowledge of what op-amps are and what they do -- now I just need to make somefin with them ! :) Thanks again everyone.

- Happs
 

Thread Starter

happs

Joined Feb 27, 2005
24
Hey peeps :)

Wow, thankyou everyoen for the great replies to this message. It really is great to be in a forum where help is at hand. The sites that have been posted are great and I have a much MUCH better understanding of what op amps actually do and how they work now :) Thankyou SO SO much.

I do have another question and I guess I should ask it in this thread since I already started it! Heheh ... This one is about clocks and timing.
From what I have learnt I have managed to make some pretty nifty little LED effects and pretty lights. I have also learnt about the 4017 decade counter and the 4060 binary counter; I would like to make some sort of clock, whether it be with 7 segment LED displays or some other method. I am sure I can work out how to wire up the IC's so they work correctly and display the time (tho not yet tried, heh) but my main query on this project is about precise timing.
I can use a 555 timer to provide the clock pulses but would this be precise enough ? It needs to be a proper 24 hour clock, so needs to be accurate, and for some reason I have a feeling that maybe a 555 timer does not provide the most accurate oscillator (oooh .. good techy word there .. heh, still learning the terms). Am I correct in thinking this, and if so, what do you guys suggest I use as a replacement ? Any other suggestions or help you can offer on this matter would be great also.

Thankyou again for all your input.

- Alex
 
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