# Understanding how to solve a logic gate when alternate gates are linked

#### Gaetano

Joined Aug 14, 2010
5
Hello All

I have no issues with understanding how to identify a logic gate on its own but when I am asked to solve a question that shows a number connected I have no idea. I have no formal training in electronics and am trying to learn by teaching myself. I have included images of two such problems below. If anyone could steer me to a book, tutorial or could explain it in layman's terms I would be really grateful, thank you
Regards
Gaetano

#### Attachments

• 33.8 KB Views: 3

#### alfacliff

Joined Dec 13, 2013
2,458
a low on a and a low on b give a high out on Q. chart b.

#### MrCarlos

Joined Jan 2, 2010
400

#### Attachments

• 90.5 KB Views: 0

#### MuPlusSigma

Joined May 22, 2014
15
If you can understand one logic gate, then you can understand multiple connected logic gates. Just start with the inputs to the circuit (A and B), and solve each individual gate one by one, determining the output of each gate based on its inputs. The output of one gate determines an input to another, until you have the state of all inputs and outputs in the circuit. Do this for every possible combination of circuit input.

These circuits might look complicated at first, but if you break it down into the individual parts you understand, you can understand the behavior of the whole circuit. With just a little practice, it should become much easier.

#### Dodgydave

Joined Jun 22, 2012
9,093
Truth table B is correct.

Replaced by single AND gate.