Limits
A pseudomorphic heterojunction bipolar transistor developed at the University of Illinois at Urbana-Champaign, built from indium phosphide and indium gallium arsenide and designed with compositionally graded collector, base and emitter, was demonstrated to cut off at a speed of 710 gigahertz.
Besides being record breakers in terms of speed, HBTs made of InP/InGaAs are ideal for monolithic optoelectronic integrated circuits. A PIN-type photo detector is formed by the base-collector-subcollector layers. The bandgap of InGaAs works well for detecting 1.55μm-wavelength infrared laser signals used in optical communication systems. Biasing the HBT to obtain an active device, a photo transistor with high internal gain is obtained. Among other HBT applications are mixed signal circuits such as analog-to-digital and digital-to-analog converters.
Read more about this topic: Heterojunction Bipolar Transistor
Famous quotes containing the word limits:
“... there are no limits to which powers of privilege will not go to keep the workers in slavery.”
—Mother Jones (1830–1930)
“The great ship, Balayne, lay frozen in the sea.
The one-foot stars were couriers of its death
To the wild limits of its habitation.
These were not tepid stars of torpid places
But bravest at midnight and in lonely spaces,
They looked back at Hans’ look with savage faces.”
—Wallace Stevens (1879–1955)
“And when discipline is concerned, the parent who has to make it to the end of an eighteen-hour day—who works at a job and then takes on a second shift with the kids every night—is much more likely to adopt the survivor’s motto: “If it works, I’ll use it.” From this perspective, dads who are even slightly less involved and emphasize firm limits or character- building might as well be talking a foreign language. They just don’t get it.”
—Ron Taffel (20th century)