Digital CMOS Abbreviation B Alphabet Dictionary
Ball Grid Array (BGA)
BGA is a type of integrated circuit packaging used for chips with a large number of pins. In BGA packages, the chip’s pins are replaced with solder balls on the bottom of the chip. These solder balls are used for mounting the chip to a circuit board using flip-chip technology, which requires specialized equipment.
Band Bending
Band bending refers to the deformation of energy levels within a semiconductor material due to the influence of built-in or external electric fields. It often occurs in doped semiconductors due to the formation of space charge regions.
Band Model
The band model is a theoretical framework used to describe the energy levels in solid-state materials, particularly semiconductors. It accounts for the formation of energy bands due to the interaction of a large number of atoms, leading to the creation of continuous energy bands rather than discrete energy levels. These bands are separated by forbidden energy gaps.
Band Tilting
Band tilting is a term applied to the linear bending of energy bands within uncharged insulators when subjected to an external electric field.
Bandgap
Bandgap refers to the energy range between the valence band and conduction band in a semiconductor material. Electrons cannot exist within this bandgap, except in certain impurity states. The bandgap energy determines the energy required to create electron-hole pairs, and for silicon, it is approximately 1.12 electron volts (eV).
Base (BJT)
In a Bipolar Junction Transistor (BJT), the base is the central region. In a PNP transistor, it is n-type, while in an NPN transistor, it is p-type. The base is typically designed to be narrow and lightly doped. It serves as the control terminal for the BJT. In the active region, the base current should be minimal, but it can be significant in saturation.
Base Transport Factor
The base transport factor in a BJT represents the ratio of majority carriers injected from the emitter into the base in the active mode that successfully reaches the collector. Ideally, this ratio should approach 1. Any injected carriers that do not reach the collector contribute to the base current.
Behavioral Simulation
Behavioral simulation is a type of simulation performed on high-level Hardware Description Language (HDL) descriptions of a digital circuit. It produces bit-accurate and cycle-accurate outputs, allowing for full functional verification of the circuit. However, it does not provide timing information, making it independent of clock periods.
Bipolar Junction Transistor (BJT)
A BJT is a type of transistor formed by combining two back-to-back asymmetric PN junctions. BJTs are used for amplification and switching. They provide a relatively high current gain but have limited integration capabilities due to base current requirements.
Bird’s Beak Pattern
The bird’s beak pattern is a triangular or prism-like shape that forms during the growth of field oxide layers in the LOCOS (Local Oxidation of Silicon) process. It occurs because oxidation tapers down toward the sacrificial nitride layer, causing the nitride to lift. The extent of the lift depends on the thickness of the field oxide, creating challenges in device feature size control.
Bistable Circuit
A bistable circuit is a digital circuit configuration in which both logic output values (high and low) are stable and can be maintained indefinitely. Common examples include flip-flops and latches, which are used for static storage in digital systems.
Bit (VHDL)
In VHDL, a bit is the default data type. It can only have two values, “1” and “0,” making it suitable for representing binary logic states. However, VHDL often uses the std_logic type, which provides more information about signal states and is preferred in most cases.
Bit-Line
A bit-line is a vertical line in a memory array that runs through a column of memory cells. Bit-lines are connected to the outputs of these cells and carry data output from memory. They are usually made of metal to minimize resistive loading and play a crucial role in read and write operations in memory devices.
Body Effect
The body effect is a secondary effect in MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) devices where the potential difference between the source and body terminals modulates the threshold voltage of the MOSFET. While the body terminals of all MOSFETs of the same type are typically shorted together, differences in source connections can lead to variations in threshold voltage, which can significantly impact device operation. This effect occurs because the source terminal affects the quasi-Fermi levels for inversion in the substrate, especially in technologies with steep retrograde doping.
Body Effect Parameter
This parameter is determined by the technology used and controls the impact of the body effect on MOSFET devices. It is typically measured in units of the square root of volts (sqrt(V)). The value of this parameter depends on factors such as the permittivity of silicon, body doping levels, and oxide capacitance per unit area.
Bohr Model
The Bohr model is a simplified atomic model that depicts an atom as having a central, immobile nucleus composed of protons and neutrons, with electrons orbiting the nucleus in discrete, circular orbits. The energy of electrons in this model takes on specific, quantized values.
Booth Encoding
Booth encoding is a method used to encode binary numbers to simplify the process of binary multiplication. It systematically encodes overlapping pairs of bits in a binary number as 0, 1, or -1. Booth encoding is particularly useful when one of the operands (multiplier) contains long sequences of 1s or 0s, as it reduces the number of operations required for multiplication.
Booth Multiplication
Booth multiplication is the multiplication operation performed when one of the operands is Booth encoded. While the multiplicand is typically left in vanilla binary form, Booth multiplication involves forming partial products not only through multiplication by 0 or 1 but also by -1. This process can be more hardware-efficient.
Boundary Scan Technique
The boundary scan technique is a testing method used for assembled systems on printed circuit boards (PCBs). It complements the scan technique and is commonly used alongside it for testing at various levels. In this technique, all pins on an integrated circuit (IC) are equipped with boundary scan registers. Additional pins, including Test Data In (TDI), Test Data Out (TDO), and Test, are used to control the scan operation. The boundary scan path connects all chips in cascade on the PCB, allowing for independent loading and unloading of pins, enhancing controllability and observability during testing.
Brent–Kung Adder
The Brent–Kung adder is a type of parallel prefix adder used in digital circuit design. It is known for its simplicity in routing compared to the Kogge–Stone adder. However, it may have a slightly higher delay and impose higher fan-out on certain stages. Despite these characteristics, Brent–Kung adders are favored for their lower area requirements.
Bridge Fault
A bridge fault is a type of coupling fault that can occur in memory cells. It is the simplest type of coupling fault, where the value stored in one memory cell inadvertently copies the value stored in another cell. This phenomenon is often caused by capacitive coupling rather than physical short defects.
Built-in Self Test (BIST)
BIST is a testing setup integrated into the hardware of a semiconductor device or chip. It allows the device to test itself without relying on external controllers. BIST typically includes components such as Automatic Test Pattern Generation (ATPG), signature analysis, and a built-in controller.
Built-in Field
A built-in field is an internal electric field present within a material. It is not generated by external sources, and as a result, the Fermi level within the material remains constant, maintaining thermal equilibrium. While no net current flows due to built-in fields, there can be current components that cancel each other out. These fields often arise due to the presence of charges in space-charge regions.
Built-in Potential
The built-in potential is an equivalent potential associated with a built-in electric field within a material. It cannot be externally measured, does not affect the Fermi level, and is not associated with net current flow. However, it manifests as band bending within the material.
Bulk Potential
Bulk potential refers to the electric potential energy difference between the Fermi level and the intrinsic Fermi level deep within the bulk of a MOSFET device.
Bundle Effort
In a gate with multiple inputs, bundle effort represents the logical effort resulting from a group of inputs that are activated simultaneously. This concept is typically applied when an input and its complement are present in the gate’s logic.
Buried Gate
A buried gate is a conceptual gate that is located below the channel region of a semiconductor device. It is not a practical structure but is used in thought experiments to understand how multi-gate transistors address issues like drain-induced barrier lowering. Unlike floating gates in Non-Volatile Memories (NVMs), buried gates are intentionally shorted to the main gate.
