Ic 555

Thread Starter


Joined Jan 27, 2012
Just to confirm my understanding about IC 555 .

When the output Q of the flip flop is high, then transistor is ON and the output is LOW ?
If the output Q of the flip flop is low, then the transistor is OFF and the output is HIGH?

So does that means the the output is follow the output of Q bar ?

Am I correct ?

I am still blur with the internal circuit of IC 555 :(


Joined Mar 24, 2008
Can you show me which internal block diagram you are referring to ? I thought after the flip flop there is an inverter logic(buffer) before the OUTPUT Pins? Like if Q= HIGH, so it will be inverted to become LOW in the OUTPUT pin ?
Try reading this article in its entirety. It was third in the list of tutorials I gave you. Reading is your friend. :D

555 Schmitt Trigger


Joined Mar 24, 2008
It is. But if you study the 555 you will find that core circuit is used in an amazing number of applications. A lot of electronics is built on previous knowledge.

The article I pointed to has the internal block diagram for a 555 laid out.

One of the things that makes the 555 special is its relatively large drive characteristics. Not too many parts can handle up to 200ma (0.2A) on the output.

Here are some other ideas you might find interesting over time.

LEDs, 555s, Flashers, and Light Chasers