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What Is The AND Gate?

Eeng.Content @Eeng.Content_2475
AND gate is among the basic logic gates. It basically consists of at least 2 inputs and one output. The figure below shows the symbol of a two-input AND gate.

AND GATE SYMBOL

A and B represent input terminals, and F represents the output terminal. The AND gate acts as a kind of multiplication. The function of the AND gate is shown as follows.

--> A.B

The observed output values change according to the values applied to the AND gate inputs. All combinations that may occur for the input and output values to be applied can be observed in the truth table given in the figure below.
TRUTH TABLE
AND GATE TRUTH TABLE EASTPAK, hosting seçimi

As can be seen from the truth table, the output value is observed as 1 in cases where both input values are 1, and 0 in other cases.

In addition, by creating the AND gate Logisim simulation program, the results can be observed by giving appropriate input and output values. The figures below show the AND gate created using the Logisim program.

AND GATE LOGISIM
AND GATE LOGISIM
AND GATE LOGISIM
AND GATE LOGISIM

Logisim is a very useful program for creating circuits with logic gates. You can see the truth table and Karnaugh map of the created circuit in the program. In addition, when you enter any Boolean algebra expression, the circuit is automatically created by the program.

The circuit elements that make up the internal structure of the AND gate are as follows:

  • Resistance
  • BJT Transistor
  • Voltage Source

The internal structure of the AND gate is shown in the figure below.

AND KAPISI İÇ YAPISI VE DEVRE GÖSTERİMİ

Here, the collector leg of the first transistor is powered by the voltage source and triggered, with this triggering the collector leg of the second transistor is also triggered. Thanks to the resistor connected to the emitter end of the second transistor, the output value is observed. Note that the 5V value in this circuit also represents 1 in the logic expression.

In addition, the function of the AND gate can be obtained by establishing an electrical circuit. The circuit elements required for this are:

  • Key
  • Voltage source
  • Lamp

The circuit is shown in the figure below.

AND KAPISI İÇ YAPISI VE DEVRE GÖSTERİMİ

A and B buttons used in the circuit represent inputs. The lamp named F represents the output. The voltage source is used as 12 Volts in the circuit. As it can be understood from the circuit, when both buttons are closed, current flows through the circuit, and thus the lamp is lit. To put it more clearly, it represents logic 1 when the buttons are closed. If it is on, it represents logic 0. We know from the function of the AND gate that the output is 1 when both inputs are 1. Similarly, when both buttons are in the logic 1 position, the lamp turns on. So it returns logic 1.

The AND internal structure and AND switching representation given above were drawn using the Proteus simulation program.

---> The OR logic gate will be explained in detail in the next article.

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