Tag Archives: Transistor

Terahertz Optical Transistors Beat Silicon


by R. Colin Johnson @ eetimes.com:

PORTLAND, Ore.–Purdue University researchers have demonstrated a CMOS-compatible all-optical transistor capable of 4THz speeds, potentially over a 1000 times faster than silicon transistors.

Nano-photonic transistors processed at low-temperatures can be fabricated atop complementary metal oxide semiconductors (CMOS) to boost switching time by ~5,000-times less than 300 femtoseconds (fs) or almost 4 terahertz (THz), according to researchers at Purdue University. The aluminum-doped zinc oxide (AZO) material from which these optical transistors are fabricated has a tunable dielectric permittivity compatible with all telecommunications infrared (IR) standards.

Terahertz Optical Transistors Beat Silicon – [Link]

Making the new silicon: Gallium nitride electronics could drastically cut energy usage


by Rob Matheson @ phys.org:

An exotic material called gallium nitride (GaN) is poised to become the next semiconductor for power electronics, enabling much higher efficiency than silicon.

In 2013, the Department of Energy (DOE) dedicated approximately half of a $140 million research institute for power electronics to GaN research, citing its potential to reduce worldwide energy consumption. Now MIT spinout Cambridge Electronics Inc. (CEI) has announced a line of GaN transistors and power electronic circuits that promise to cut energy usage in data centers, electric cars, and consumer devices by 10 to 20 percent worldwide by 2025.

Power electronics is a ubiquitous technology used to convert electricity to higher or lower voltages and different currents—such as in a laptop’s power adapter, or in electric substations that convert voltages and distribute electricity to consumers. Many of these power-electronics systems rely on silicon transistors that switch on and off to regulate voltage but, due to speed and resistance constraints, waste energy as heat.

Making the new silicon: Gallium nitride electronics could drastically cut energy usage – [Link]

Simple circuit lets you characterize JFETs


by John Fattaruso @ edn.com:

When working with discrete JFETs, designers may need to accommodate a large variation in device parameters for a given transistor type. A square-law equation is usually used as an approximate model for the drain-current characteristic of the JFET: ID=β(VGS−VP)2, where ID is the drain current, VGS is the gate-to-source voltage, β is the transconductance parameter, and VP is the gate pinch-off voltage. With this approximation, the following equation yields the zero-bias drain current at a gate-to-source voltage of 0V: IDSS=βVP 2, where IDSS is the zero-bias drain current.

Simple circuit lets you characterize JFETs – [Link]

IBM shows working devices fabricated at 7nm node


by Graham Prophet @ edn-europe.com:

An alliance led by IBM Research, together with New York academic institution SUNY Polytech and with Samsung and GlobalFoundries, has produced 7nm (nanometer) node test chips with functioning transistors.

Continuing semiconductor scaling down to feature sizes of 7 nm is expected to yield further gains in performance, and lower power levels, but in IBM’s words, “[its] researchers had to bypass conventional semiconductor manufacturing approaches”. The finFET-style transistors in the demonstrator were constructed with silicon-germanium (SiGe) channels, and the lithography that defined them employed Extreme Ultraviolet (EUV) technology, “at multiple levels”. [That is, the use of EUV was not reserved for definition of a single critical part of the transistor structure.]

IBM shows working devices fabricated at 7nm node – [Link]

EEVblog #748 – How Do Transistors Work?

Dave explains how BJT and MOSFET transistors work at the silicon chip level.
How does a BJT transistor actually amplify current?
P and N type doping, charge carriers, conduction channel, field effect, holes and electrons, all the other good stuff.

EEVblog #748 – How Do Transistors Work? – [Link]

LDMOS Transistor Bias Control in RF Power Amplifiers


Nowadays, laterally diffused metal oxide semiconductor (LDMOS) transistors are widely used for RF Power Amplification and in many applications. A simplified circuit of an LDMOS amplifier bias circuit is shown in the schematic diagram above. The DC Bias on these amplifiers is set by applying a DC voltage to the gate (VGS) and by monitoring the Drain current (IDD). Ideally, this IDD will be constant over temperature, but since the VGS of LDMOS amplifier devices varies with temperature, some type of temperature compensation is required.

The ISL21400 features a precision voltage reference combined with a temperature sensor whose output voltage varies linearly with temperature. The precision 1.20V reference has a very low temperature coefficient, and its output voltage is scaled by an internal DAC (VREF) to produce a temperature stable output voltage that is programmable from 0V to 1.20V. The output voltage from the temperature sensor (VTS) is summed with VREF to produce a temperature dependent output voltage. The maximum voltage supply of the ISL21400 is 5.5V, and the LP2950 voltage regulator drops the LDMOS voltage to 5.5V for the ISL21400 supply. An LC filter is then added to the output of the voltage regulator to ensure no RF energy present on the supply line. The ISL21400 can be tied to a microcontroller or to any I/O connector for PC control and programming.

The RFPA bias control using the ISL21400 is very straightforward. The RFPA uses the Freescale AFT21S140W02GSR3. LDMOS are useful devices for many applications including commercial FM broadcasting and TV power transmitters, cellular and paging communication systems, and military RF and microwave hand-held transceivers.

LDMOS Transistor Bias Control in RF Power Amplifiers – [Link]

Scientists Pursue Super-Fast Material


by R. Colin Johnson @ eetimes.com:

PORTLAND, Oregon — Scientists trying to fulfill the 80-year-old dream of Nobel laureate Eugene Wigner, recently discovered how to place crystalline lattices of pure electrons in the bottom of a silicon-encased quantum well. The resulting material promises electron mobility more than 200 times greater than that of graphene and more than 1,700 times that of crystalline silicon.

So far, the work is still at the level of fundamental physics, but if researchers make the kind of advances they anticipate they could open a door to significant applications in semiconductors.

Scientists Pursue Super-Fast Material – [Link]

Basics of a Vbe Multiplier: what it is, how it works & where it is used

by w2aew @ youtube.com

The Vbe Multliplier circuit, also known as an Amplified Diode or Adjustable Diode, is a useful circuit that allows you to set a user desired voltage drop without using a series combination of diodes or zeners. This video describes and demonstrates how this circuit works, and shows a few applications where it is used. It is commonly used to set the bias on a low-impedance push-pull output stage of an amplifier. All transistors shows are typical general purpose devices like the 2N3904/2N3906. The scope is being used as a simple curve tracer in the first part of the video.

Basics of a Vbe Multiplier: what it is, how it works & where it is used – [Link]

Voltage indicator transitions between colours


by Einar Abell @ edn.com:

This Design Idea gives two versions of an indicator light that changes from green to red as a battery discharges. There are many circuits that do this sort of thing, but all the ones I have seen are too complex and costly for my taste. This DI shows a method that uses an absolute minimum of low cost parts: a dual-color LED and four other parts.

Voltage indicator transitions between colours – [Link]