Gates
This section describes schematic symbols for gates. CLICK HERE IF YOU CAME FROM A WEB SEARCH
- AND Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A AND gate is a gate whose output goes to a digital 1 (or on, or high, etc.) when both inputs are 1. On the schematic, the inputs are the two connections on the flat side of the symbol. The output is the connection on the rounded part. The inputs are usually refered to as A and B. A is on the top. Remember that with gates, the symbol always points towards the outputs. The truth table for an AND gate is shown below:
| A |
B |
Output |
| 0 |
0 |
0 |
| 1 |
0 |
0 |
| 1 |
1 |
1 |
0 |
1 |
0 |
- NAND Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A NAND gate is a gate whose output goes to a digital 0 (or off, or low, etc.) when both inputs are 1. On the schematic, the inputs are the two connections on the flat side of the symbol. The output is the connection on the rounded part. The inputs are usually refered to as A and B. A is on the top. Remember that with gates, the symbol always points towards the outputs. The truth table for an NAND gate is shown below:
| A |
B |
Output |
| 0 |
0 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
0 |
0 |
1 |
1 |
- OR Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A OR gate is a gate whose output goes to a digital 1 (or on, or high, etc.) if one or both inputs are 1. On the schematic, the inputs are the two connections on the slightly curved side of the symbol. The output is the connection on the pointed part. The inputs are usually refered to as A and B. A is on the top. Remember that with gates, the symbol always points towards the outputs. The truth table for an OR gate is shown below:
| A |
B |
Output |
| 0 |
0 |
0 |
| 1 |
0 |
1 |
| 1 |
1 |
1 |
0 |
1 |
1 |
- NOR Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A NOR gate is a gate whose output goes to a digital 0 (or off, or low, etc.) if one or both inputs are 1. On the schematic, the inputs are the two connections on the slightly curved side of the symbol. The output is the connection on the pointed part. The inputs are usually refered to as A and B. A is on the top. Remember that with gates, the symbol always points towards the outputs. The truth table for an NOR gate is shown below:
| A |
B |
Output |
| 0 |
0 |
1 |
| 1 |
0 |
0 |
| 1 |
1 |
0 |
0 |
1 |
0 |
- Exclusive OR (XOR) Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A XOR gate is a gate whose output goes to a digital 1 (or on, or high, etc.) if one but not both inputs are 1. On the schematic, the inputs are the two connections on the slightly curved side of the symbol. The output is the connection on the pointed part. The inputs are usually refered to as A and B. A is on the top. Remember that with gates, the symbol always points towards the outputs. The truth table for an XOR gate is shown below:
| A |
B |
Output |
| 0 |
0 |
0 |
| 1 |
0 |
1 |
| 1 |
1 |
0 |
0 |
1 |
1 |
- Exclusive NOR (XNOR) Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A XNOR gate is a gate whose output goes to a digital 0 (or off, or low, etc.) if one but not both inputs are 1. On the schematic, the inputs are the two connections on the slightly curved side of the symbol. The output is the connection on the pointed part. The inputs are usually refered to as A and B. A is on the top. Remember that with gates, the symbol always points towards the outputs. The truth table for an XNOR gate is shown below:
| A |
B |
Output |
| 0 |
0 |
1 |
| 1 |
0 |
0 |
| 1 |
1 |
1 |
0 |
1 |
0 |
- Inverter (NOT) Gate
- Gates are the building blocks that all digital integrated circuits are built on. Gates are simple circuits that perform logical opetations. A NOT gate is a gate whose output goes to a digital 1 (or on, or high, etc.) when the input is at 0. In other words, it inverts the input. On the schematic, the input is the connection on the flat side of the symbol. The output is the connection on the pointed part. Note that a NOT gate without a circle on the output is referred to as a buffer, and just passes the input unchanged to the output. Remember that with gates, the symbol always points towards the outputs. The truth table for a NOT gate is shown below:
- SR Flip Flop
- A flip flop is a gate whose output(s) alternate between 1 and 0 with input pulses. In the case of an SR flip flop, the Q and NOT Q (the Q with the line over it) alternate with different inputs on the R and S lines. The truth table below should explain:
| R |
S |
Q |
NOT Q |
| 0 |
0 |
disallowed |
| 1 |
0 |
1 |
0 |
| 1 |
1 |
no change |
0 |
1 |
0 |
1 |
- JK Flip Flop
- A flip flop is a gate whose output(s) alternate between 1 and 0 with input pulses. In the case of an JK flip flop, the Q and NOT Q (the Q with the line over it) alternate with different inputs on the R and S lines. A JK flip flop allows both outputs to be high at the same time. Also, a JK flip flop waits for a clock signal to change the outputs. The truth table below should explain:
| R |
S |
Q |
NOT Q |
| 0 |
0 |
no change |
| 1 |
0 |
1 |
0 |
| 1 |
1 |
Toggle |
0 |
1 |
0 |
1 |
- T Flip Flop
- A flip flop is a gate whose output(s) alternate between 1 and 0 with input pulses. In the case of an T flip flop, the Q and NOT Q (the Q with the line over it) alternate with pulses on the T line. For example, the first pulse will cause Q to go high and NOT Q to go low. On the second pulse, Q goes low and NOT Q goes high. The cycle repeats with every pulse.
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