In theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathematical model for digital logic circuits. Circuits are defined by the gates they contain and the values the gates can produce. For example, the values in a Boolean circuit are Boolean values, and the circuit includes conjunction, disjunction, and negation gates. The values in an integer circuit are sets of integers and the gates compute set union, set intersection, and set complement, as well as the arithmetic operations addition and multiplication.
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š Digital circuit in the context of Formal verification
In the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of a system with respect to a certain formal specification or property, using formal methods of mathematics. Formal verification is a key incentive for formal specification of systems, and is at the core of formal methods.It represents an important dimension of analysis and verification in electronic design automation and is one approach to software verification. The use of formal verification enables the highest Evaluation Assurance Level (EAL7) in the framework of common criteria for computer security certification.
Formal verification can be helpful in proving the correctness of systems such as: cryptographic protocols, combinational circuits, digital circuits with internal memory, and software expressed as source code in a programming language. Prominent examples of verified software systems include the CompCert verified C compiler and the seL4 high-assurance operating system kernel.
In this Dossier
- ā Core Definition: Digital circuit
- š Digital circuit in the context of Formal verification
- Digital circuit in the context of NMOS logic
- Digital circuit in the context of Mixed-signal
- Digital circuit in the context of Arithmetic logic unit
- Digital circuit in the context of Resistorātransistor logic
- Digital circuit in the context of Diodeātransistor logic
Digital circuit in the context of NMOS logic
NMOS or nMOS logic (from N-type metalāoxideāsemiconductor) uses n-type (-) MOSFETs (metalāoxideāsemiconductor field-effect transistors) to implement logic gates and other digital circuits.
NMOS transistors operate by creating an inversion layer in a p-type transistor body. This inversion layer, called the n-channel, can conduct electrons between n-type source and drain terminals. The n-channel is created by applying voltage to the third terminal, called the gate. Like other MOSFETs, nMOS transistors have four modes of operation: cut-off (or subthreshold), triode, saturation (sometimes called active), and velocity saturation.
Digital circuit in the context of Mixed-signal
A mixed-signal integrated circuit is any integrated circuit that has both analog circuits and digital circuits on a single semiconductor die. Their usage has grown dramatically with the increased use of cell phones, telecommunications, portable electronics, and automobiles with electronics and digital sensors.
Digital circuit in the context of Arithmetic logic unit
In computing, an arithmetic logic unit (ALU) is a combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit (FPU), which operates on floating point numbers. It is a fundamental building block of many types of computing circuits, including the central processing unit (CPU) of computers, FPUs, and graphics processing units (GPUs).
The inputs to an ALU are the data to be operated on, called operands, and a code indicating the operation to be performed (opcode); the ALU's output is the result of the performed operation. In many designs, the ALU also has status inputs or outputs, or both, which convey information about a previous operation or the current operation, respectively, between the ALU and external status registers.
Digital circuit in the context of Resistorātransistor logic
Resistorātransistor logic (RTL), sometimes also known as transistorāresistor logic (TRL), is a class of digital circuits built using resistors as the input network and bipolar junction transistors (BJTs) as switching devices. RTL is the earliest class of transistorized digital logic circuit; it was succeeded by diodeātransistor logic (DTL) and transistorātransistor logic (TTL).
RTL circuits were first constructed with discrete components, but in 1961 it became the first digital logic family to be produced as a monolithic integrated circuit. RTL integrated circuits were used in the Apollo Guidance Computer, whose design began in 1961 and which first flew in 1966.
Digital circuit in the context of Diodeātransistor logic
Diodeātransistor logic (DTL) is a class of digital circuits that is the direct ancestor of transistorātransistor logic. It is called so because the logic gating functions AND and OR are performed by diode logic, while logical inversion (NOT) and amplification (providing signal restoration) is performed by a transistor (in contrast with resistorātransistor logic (RTL) and transistorātransistor logic (TTL).