Transistors are OFF Therefore the output Y is logic 1. Itġ) When A=0 and B=0 both the PMOS transistors are on and both the NMOS Mainly the voltage drop across the pull-up resistor connected as shown inįigure above shows the CMOS implementation of the two input AND gate. Output is open circuited to Input1 and the output is open circuited to OFF and the other diode which is connected to Input2 is OFF. The output=0.Ĥ) When Input1=1 and Input2=1 one diode is which is connected to Input1 is Output is open circuited to Input1 and the output is short circuited to OFF and the other diode which is connected to Input2 is ON. The output =0.ģ) When Input1=1 and Input2=0 one diode is which is connected to Input1 is Output is short circuited to Input1 and the output is open circuited to ON and the other diode which is connected to Input2 is OFF. The output =0.Ģ) When Input1=0 and Input2=1 one diode is which is connected to Input1 is Therefore, since both Input1 and Input2 are at logic 0. Short circuited to Input1 and the output is also short circuited to Input2. It consists of two diodesġ) When Input1=0 and Input2=0 both the diodes are ON. Figure below shows the wired AND gate circuit.įigure above shows the wired AND gate circuit. Or greater than that of the source is applied to all inputs the source Voltage from the source is directed away from the output through diodesĬonnected directed towards the inputs. Resistor and one diode per input to create this function. A wired logicĬonnection can create an AND gate. Using only passive components such as diodes and resistors. Here, A and BĪre input logic variables and X is the output.Ī wired logic connection is a logic gate that implements Boolean logic Independent logic variables A and B is written as X = A.B. The logic symbol and truth table ofĪ two-input AND gate are shown in Figure. InĪll other cases, the output is logic 0. The output of theĪND gate is a logic 1 only when all of its inputs are in logic 1 state. The output of an AND gate is HIGH only when all the inputs are in Since low voltage levels help to produce voltage swings, this type of logic may be called low-level logic (LLL).An AND gate is a logic gate in which two or more inputs and one output is To increase the noise immunity, we may add more diodes in series with D3. 3.2 performs the basic two-input NAND function. The operations described here suggest that the circuit shown in Fig. This turns off T making Z = +VCC= logic 1. Therefore, when A = 0 and B = 0, A = 0 and B = 1, or B = 0 and A = 1, one or both of the diodes conduct, which make the diode D3 reverse biased. This makes output Z = VCES = +0.2 V, where VCES = collector-emitter saturation voltage. When both D1 and D2 are OFF (i.e., A = B = 1), D3 gets forward biased and turns on transistor T. The addition of D3 ensures more speedy switching operation. To ensure proper operation of the circuit a diode D3 is also added, as shown in Fig. Transistor T inverts the AND function to produce the NAND function. 3.2, the diodes D1 and D2 perform the AND operation. The DL gate with the addition of one transistor is called as the DTL (diode-transistor logic) gate. Hence to produce inversion, we connect a transistor in series with the diodes as shown in Fig. However, we require gates with negation such as NAND and NOR to generate all types of logic functions can be derived using either of these gates alone (see previous blog page). The DL gates have the major defect that they cannot perform inversion (NOT operation).
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