AC coupled ?? DC coupled?? What??

ac couple dc couple

From my previous op amp building experience (which i post earlier), I know that I need to follow the datasheet, and build my circuit according to the schematics that's shown on the datasheet.

Here's my question tho:
When I was in school, I thought an inverting amp was just an op amp with two resistors, but when i tried to build the inverting amp this way, it didn't work for me. Then I followed the schematic that's on the LM324, it's called AC Coupled Inverting Amplifier (page 14 of the attachment). It works!!! They added a few capacitors. And when I feed in my sin wave as the input, i can what i want. So my questions are:
1) Why do we need to add those capacitors? Why it doesn't work if i don't add them?
2) What's AC coupling?? Was the one that i learn from school DC op amp?
3) Does the value of the capacitors matter?? if it does, how? the bigger the better? haha...

Sorry, I'm new... I wish I had paid more attention when i was still in school. Thanks in advance. Any suggestion/advice are welcome.

ac coupled dc coupled

Search Edaboard for "Opamps for everyone", you will find a link for book that explains in detail what you need to know to understand how opamps work. AC coupled means it can amplify only alternating signal, not DC. If you attach battery on input, output will swing only for short time and drop down to 0. You should also find some elementary books that explain RC RL and LC networks to understand how components surrounding opamps behave. Browse through section for books on EDA to find beginers books for electronics.

ac coupled inverting amp

I don't think an inverting amplifier must have capacitors. Maybe there is so large DC offset in your input signal that the circuit can't work properly unitil you correctly configure your circuit.

ac coupling

agree to mengly,
i think the dc offset in your circuit has been amplify by the amp to its limitation, so u can not dector the amplified AC signal~

dc coupled inverting amplifier

manofwax,
You don't mention whether you are using a single supply or not. If you are using dual supplies (+ and - supplies) you do not need the capacitors. However, if you are using a single supply, then when the AC input goes negative, the Op Amp substrate diode gets forward biased, and the op-amp will not function. The voltage divider on the + input provides a "pseudo ground" that is equal to half the supply voltage. The 10uf capacitor C2 ensures that the AC impedance of the "pseudo ground" with respect to the power supply common is low. Its value is not critical. By capacitor coupling the input, you are ensured that the input voltage never goes below the negative supply vootage, which is zero for the single supply case.
Regards,
Kral