Sr flip flop pdf

Hi guys, in this tutorial I will show you some NPN transistor based logic gates. These sr flip flop pdf are extremely easy to understand. I think if you know a little bit about NPN transistors, you will be fine. The use of transistors for the construction of logic gates depends upon their utility as fast switches.

When the base-emitter diode is turned on enough to be driven into saturation, the collector voltage with respect to the emitter may be near zero and can be used to construct gates for the TTL logic family. I am going to show the logic gate’s symbols, truth tables and schematics. I will also show this circuits on the breadboard. There is a small text and a gif for every logic gate. I attached three images for beginners.

The third image is the most important. A NOT gate is often referred to an inverter. Inverters simply output the opposite as the input. The AND gate is a logic Boolean gate that represents multiplication in basic algebra. This is the equivalent of a multiplication statement where only Boolean variables are allowed. For the AND logic, the transistors are in series and both transistors must be in the conducting state to drive the output high. A NAND gate is also referred to as a NEGATED AND gate.

It is the opposite or inverse of a simple AND gate. For the NAND logic, the transistors are in series, but the output is above them. The output is high unless both A and B inputs are high, in which case the output is taken down close to ground potential. In the simulator I accidentally used a 200Ohm resistor, but in reality you should use around 1K or something like that. The OR gate is a logic Boolean gate that represents addition in basic algebra. This closely resembles the addition statement where only Boolean variables are allowed.

For the OR logic, the transistors are in parallel and the output is driven high if either of the transistors is conducting. A NOR gate is also referred to as a NEGATED OR gate. It is the opposite or inverse of a simple OR gate. For the NOR logic, the transistors are in parallel with the output above them so that if either or both of the inputs are high, the output is driven low. In the simulator I used a 200 Ohms resistor, but you should use one around 1K. A XOR gate is also referred to as EXCLUSIVE OR. As you can see I constructed this one with other gates.

In this circuit I used a NAND, OR and an AND gate. A XNOR gate, like the XOR gate, is also referred to EXCLUSIVE NOR. This is similar to the XOR gate but is inverted. I used two inverter, two AND and an OR gate in this circuit. Now we know the transistor gates, lets make something with them. For example, here is an SR flip-flop. When using static gates as building blocks, the most fundamental latch is the simple SR latch, where S and R stand for set and reset.

It can be constructed from a pair of cross-coupled NOR logic gates. The stored bit is present on the output marked Q. The output usually marked as Q, but sometimes it is marked as X, Y or F. While the S and R inputs are both low, feedback maintains the Q and Q’ outputs in a constant state, with Q’ the complement of Q. R is pulsed high while S is held low, then the Q output is forced low, and stays low when R returns to low.

First of all, build two independent NOR gate on your breadboard. Do not connect both of their inputs the the push buttons, you only have to connect the A inputs of each gate. Now connect the B inputs to the other NOR gate’s output trough a 10k resistor. Now we are ready, you made an SR flip-flop or SR latch. When you press the button one, the Q LED goes out, and the Q’ LED lights up.

Then if you press the button two, the Q LED light up, and the Q’ goes out. Technically you can store data with it, this is why we call it “latch”. You shouldt press the two buttons at once, its a forbidden state, it can make the flip-flop unstable. We have a be nice policy. I am in need of a not gate and started by using a pn2222 transistor.