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An SR latch constructed from cross-coupled NAND gates. The circuit shown below is a basic NAND latch. The inputs are also generally designated S and R for Set and Reset respectively. Because the NAND inputs must normally be logic 1 to avoid affecting the latching action, the inputs are considered to be inverted in this circuit (or active low).
A CMOS transistor NAND element. V dd denotes positive voltage.. In CMOS logic, if both of the A and B inputs are high, then both the NMOS transistors (bottom half of the diagram) will conduct, neither of the PMOS transistors (top half) will conduct, and a conductive path will be established between the output and Vss (ground), bringing the output low.
dual 4-input NAND gate Schmitt trigger 14 SN74LS18: 74x19 6 hex inverter gate Schmitt trigger 14 SN74LS19: 74x20 2 dual 4-input NAND gate 14 SN74LS20: 74x21 2 dual 4-input AND gate 14 SN74LS21: 74x22 2 dual 4-input NAND gate open-collector 14 SN74LS22: 74x23 2 dual 4-input NOR gate with strobe, one gate expandable with 74x60 16 SN7423: 74x24 4
The NAND gate has the property of functional completeness, which it shares with the NOR gate. That is, any other logic function (AND, OR, etc.) can be implemented using only NAND gates. [2] An entire processor can be created using NAND gates alone. In TTL ICs using multiple-emitter transistors, it also requires fewer transistors than a NOR gate.
In order to complete the excitation table of a flip-flop, one needs to draw the Q(t) and Q(t + 1) for all possible cases (e.g., 00, 01, 10, and 11), and then make the value of flip-flop such that on giving this value, one shall receive the input as Q(t + 1) as desired.
This dual threshold action is called hysteresis and implies that the Schmitt trigger possesses memory and can act as a bistable multivibrator (latch or flip-flop). There is a close relation between the two kinds of circuits: a Schmitt trigger can be converted into a latch and a latch can be converted into a Schmitt trigger.
The first part number in the series, the 7400, is a 14-pin IC containing four two-input NAND gates. Each gate uses two input pins and one output pin, with the remaining two pins being power (+5 V) and ground. This part was made in various through-hole and surface-mount packages, including flat pack and plastic/ceramic dual in-line.
This is because the RS latch is plagued by the undefined condition which is resolved in the JK and D latches. The sequence is natural. 15. The NAND implementation of the gated SR latch is not shown and it should be for completeness and consistency. 16. The image entitled "A JK flip-flop made of NAND gates" is horrendous.