Digital CMOS Abbreviation H Alphabet Dictionary
H Tree
A clock distribution network is used in integrated circuits, especially for synchronous designs. It features branches that resemble the letter “H” and allows for a regular fractal distribution of clock signals, inheriting the advantages of various clock tree topologies.
Half Adder
A fundamental building block for adders, which accepts two inputs and produces two outputs: a sum and a carry. While less versatile than full adders, half adders are used to optimize certain arithmetic circuits, such as array multipliers. They consist of two relatively independent CMOS gates: a sum gate and a carry gate.
HDL (Hardware Description Language)
A set of languages used to describe digital circuits. HDLs enable designers to specify the behavior and structure of hardware components. They differ from programming languages as they focus on concurrent descriptions of hardware interconnections rather than sequential operations.
Heterojunction
A semiconductor junction where two regions consist of different materials with the potential for differential doping. In heterojunctions, the equilibrium band diagram often exhibits discontinuities in the conduction band and valence band edges due to differing electron affinities between the materials.
Hierarchical Design
Also known as bottom-up design, it involves creating larger electronic designs by assembling smaller building blocks or modules. This approach allows for complex circuits to be managed and implemented more efficiently. Debugging and modification are simplified because changes can be made to a single location without affecting all instances of a component.
High-Impedance Node
A node in an electronic circuit that has no low-impedance paths connected to either the power supply or ground. High-impedance nodes can store values, but any loss of charge at these nodes is irreparable. They may transition between high and low impedance states based on circuit operation.
Hold-Time
The duration after the active edge of a clock signal during which the input of a flip-flop or register must remain stable. Hold-time ensures that data stored in the register is not corrupted due to any clock overlap or setup-time violations.
Hold-Time Violation
A condition where the input of a flip-flop or register changes too soon after the active edge of the clock signal, such that the required hold-time is not met. These violations can occur due to fast combinational paths and may require designer intervention to add delay to the offending path.
Hole
An empty state in the valence band of a semiconductor. Under the influence of an electric field, valence electrons can move into this empty state, effectively creating a positively charged carrier. Holes move in the direction of the electric field.
Hole Current
Current resulting from the motion of holes (positive charge carriers) in the valence band of a semiconductor, whether due to drift or diffusion.
Homojunction
A semiconductor junction where both sides consist of the same material, differing only in the type and/or concentration of dopants. In thermal equilibrium, all energy levels are continuous (though not necessarily flat) across the junction.
Hot Carrier Effect
An effect is observed in transistors, particularly velocity-saturated transistors, where carriers (electrons) reach their maximum kinetic energy at the drain terminal. In some cases, highly energetic electrons near the drain can overcome the oxide barrier, potentially leading to device performance degradation. In nonvolatile memories, the hot carrier effect can be intentionally used for programming.
Hybrid Clock Network
A clock distribution network that combines multiple clock distribution methods to leverage their respective advantages. For example, a combination of a spine network, tree network, and alpha grid may be used to efficiently distribute clock signals in different regions of a chip.
