UNIT 6 BASIC DIGITAL Electronics

Breadboard

A circuit board for wiring temporary circuits, usually used for prototypes or laboratory work.

Digital Signal

A digital signal refers to an electrical signal that is converted into a pattern of bits. Unlike an analog signal, which is a continuous signal that contains time-varying quantities, a digital signal has a discrete value at each sampling point

Transistor-Transistor (TTL)

A family of digital logic devices whose basic element is the bipolar junction transistor.

Truth Table

A list of all possible input values to a digital circuit, listed in ascending binary order, and the output response for each input combination.

Cycle

A series of events that are regularly repeated in the same order.

Digital Waveform

A series of logic 1s and 0s plotted as a function of time.

Dual-Inline-Package (DIP)

A very common IC package with two parallel rows of pins intended to be inserted into a socket of through holes drilled in a printed circuit board.

NOT GATE

Also called an INVERTER gate or an inverting buffer. A logic gate that changes its input logic level to the opposite state.

Analog Signal

An analog signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. ... For example, an aneroid barometer uses rotary position as the signal to convey pressure information.

Logic Gate

An electronic circuit that performs a Boolean algebraic function.

Shift Register

Digital circuit that accepts binary data from some input source and then shifts these data through a chain of flip-flops one bit at a time. Think about how a Calculator works as you add digits.

AND GATE

Digital circuit that implements the AND operation. The output of this circuit is HIGH only if all of its inputs are HIGH.

OR GATE

Digital circuit that implements the OR operation. The output of this circuit is HIGH (logic level 1) if any or all of its inputs are HIGH.

Combinational Logic

Digital circuitry in which an output is derived from the combination of inputs, independent of the order in which they are applied.

Sequential Logic

Digital circuitry in which the output state of the circuit depends not only on the states of the inputs, but also on the sequence in which they reached their present states.

Clock

Digital signal in the form of a rectangular pulse train or a square wave.

Boolean Logic

Named after the nineteenth-century mathematician George Boole, Boolean logic is a form of algebra in which all values are reduced to either TRUE or FALSE. Boolean logic is especially important for computer science because it fits nicely with the binary numbering system, in which each bit has a value of either 1 or 0.

D Flip-Flop

The D flip-flop captures the value of the D-input at a definite portion of the clock cycle (such as the rising edge of the clock). That captured value becomes the Q output. At other times, the output Q does not change. The D flip-flop can be viewed as a memory cell.

XOR Gate

The XOR gate (sometimes EOR gate, or EXOR gate and pronounced as Exclusive OR gate) is a digital logic gate that gives a true (1 or HIGH) output when the number of true inputs is odd or different. An XOR gate implements an exclusive or; that is, a true output results if one, and only one, of the inputs to the gate is true. Sometimes called a difference engine.

Kirchoff's Current Law (Junction Law)

The algebraic sum of all currents into and out of any branch point in a circuit must equal zero.

Kirchoff's Voltage Law (Loop Law)

The algebraic sum of all voltages around any closed path must equal zero.

Conventional Current

The direction of current flow associated with positive charge in motion. The current flow direction is from a positive to negative potential, which is in the opposite direction of electron flow.

Logic HIGH

The higher of two voltages in a digital system with two logic levels.

Logic LOW

The lower of two voltages in a digital system with two logic levels.

Rising Edge

The part of a pulse where the logic level is in transition from a LOW to a HIGH.

Asynchronous Counter

Type of counter in which each flip-flop output serves as the clock input signal for the next flip-flop in the chain.