The symbol is an AND gate with a small circle on the output. The outputs of all NAND gates are high if any of the inputs are low. This is a NOT-AND gate which is equal to an AND gate followed by a NOT gate. In this way, the output is high when the input is low and low when the input is high. This ground path creates a shortcut that bypasses the output, which causes the output to go low. When voltage is present at the input, the transistor turns on, allowing current to flow through the collector-emitter circuit directly to ground. In this way, the circuit’s output is high when its input is low. Thus, current from the supply voltage (Vcc) flows through resistor R1 to the output.

When the transistor is off, no current flows through the collector-emitter path. When no voltage is present on the input, the transistor turns off. NOT gate can be realized through transistor.The input is connected through resistor R2 to the transistor’s base. This is also shown as A' or A with a bar over the top, as shown at the outputs. If the input variable is A, the inverted output is known as NOT A. The NOT gate is an electronic circuit that produces an inverted version of the input at its output. So, if any or both inputs are high, the output will be high or “1”. Hence at output we get high or logic 1 or +5V.

Since this time anode is at high voltage than cathode therefore current will flow through forward biased diode and this current then appears on resistor causing high voltage at output terminal also. When either of the diodes is at logic 1 or high state then the diode corresponding to that input is forward bias. Since the anode terminal of diode is at lower voltage level than the cathode terminal, so diode will act as open circuit so there is no voltage across resistor and hence output voltage is same as ground. When both the inputs are at logic 0 or low state then the diodes D1 and D2 become reverse biased. In this case, we have taken two inputs which can be seen in the circuit below. The anode part of diode is connected with input while the cathode part is joined together and a resistor, connected with the cathode is grounded. To realise OR gate, we will use a diode at every input of the OR gate. Presently, we will learn how to implement the OR gate using DRL (Diode-Resistance-Logic). OR gate can be realized by DRL (Diode-Resistance-Logic) or by TTL (Transistor-Transistor-Logic). A plus (+) is used to show the OR operation. The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high. Both transistors must be saturated “ON” for an output at Q. A.B or can be written as ABĪ simple 2-input logic AND gate can be constructed using RTL (Resistor-Transistor-Logic) switches connected together as shown below with the inputs connected directly to the transistor bases. A dot (.) is used to show the AND operation i.e. The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high. The relationship between the input and the output is based on a certain logic. Logic gates are electronic circuits having one or more than one input and only one output. Logic gates are the basic building blocks of any digital system. Verification and interpretation of truth table for AND, OR, NOT, NAND, NOR, Ex-OR, Ex-NOR gates.

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