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This DC-DC Converter start-up from as low as 330mV input! Marian Stofka writes:
The bq25504 from Texas Instruments is a good candidate to become a milestone on the road to micro-power management and energy harvesting. A prominent feature of this IC is its ability to start up at a supply voltage as low as 330 mV typically, and 450 mV guaranteed. With an SMD inductor and a few capacitors and resistors, it forms a dc-dc converter with a high power efficiency that is unprecedented, especially in the ultralow-power region.
DC-DC converter starts up and operates from a single photocell - [Link]
Fully depleted silicon transistor are much promising for future developments. Xavier Cauchy writes:
To date, transistor scaling has continued in accordance with Moore’s Law down to 32 nm. Engineering challenges, however, are forcing chipmakers to compromise performance and power efficiency in order to reach smaller nodes – unless they switch to new technologies that help better solve these challenges. Today, the semiconductor industry is starting to deploy such new technologies, largely relying on “fully-depleted” transistors for continued scaling and performance gains.
Fully depleted silicon technology to underlie energy-efficient designs at 28 nm and beyond - [Link]
Re:load is an adjustable constant current load with the following properties:
- No external power supply required – powered by the device under test
- Wide range of input voltages, from 3.3 volts to 32 volts
- Adjustable load from 0 to 3.5 amps
- Up to 14 watts power dissipation (with design heatsink)
- Virtually indestructable: The power FET, BTS117, has built in overtemp, ESD, and overcurrent protection
- Load remains constant under different input voltages – 40 milliamp variation over input voltage range
- Screw terminal and banana plug footprints
- Low BoM cost, and easy to solder thru-hole parts
- Test points for reading current with a voltmeter
A simple, flexible adjustable dummy load - [Link]
BF245, a JFET transistor produced for many decades by several companies, has joined the list of discontinued components. However an equivalent replacement exists in an SMT package and its name is BF545.
BF245 in a TO-92 package has been one of the first transistors, which were mass-used. That’s why it’s no wonder, that the BF 245 is nowadays familiar to every experienced technician. As a transistor with a very high input resistance (tens of MOhm) and a relativlely low noise, it’s gained a global popularity and served to many beginning technicians at an assembly of their first radio-receivers. There are many other FET transistors on the market nowadays, thus the usage of BF245 is substantially smaller. Moreover, a majority of electronics is produced with SMT components, what probably was one of more reasons why all main producers have discontinued the BF245.
However, BF245 is still an interesting transistor, that’s why it will be henceforward available in a SOT23 SMT package as the BF545. It is available in 3 groups A, B, C – sorted according to IDSS at VGS=0. Directly from our stock are available BF545A, BF545B and BF545C from company NXP (originally Philips). Detailed information can be found in the BF545 datasheet, as well as in the RF Manual document.
BF245 – the legend is leaving, the successor comes - [Link]
Here is a reference design from Maxim how to built a circuit that would seamlessly switch to the secondary power supply if the primary fails. [via]
This power-supply sequencer senses a loss of the main supply voltage and, by controlling the two FETs, automatically switches the load to the secondary (backup) supply.
The FET-OR connection for power supplies - [Link]
scd writes:
I designed this controller for my Crystalite Sparrow 48V electric bicycle hub motor. The core function of a DC motor controller is to periodically read the throttle setting and adjust the current being supplied to the motor. It does this with a technique called pulse-width modulation or PWM (more on this later). Other functions of the controller include: 1) low-voltage cutoff .. monitor the battery voltage and shut down the motor if the battery voltage is too low .. this protects the battery from over-discharge. 2) over-temperature cutoff .. monitor the temperature of the FET power transistors and shut down the motor if they become too hot .. this protects the FET power transistors. 3) over-current cutoff .. reduce the current to the motor if too much current is being supplied .. this protects both the motor and the the FET power transistors. 4) brake cutoff .. shut down the motor when the brake is applied .. this is a safety feature .. if the user applies brake and throttle, the brakes win.
DC Motor Controller for Electric Bicycle - [Link]
www.adafruit.com writes:
Having a hard time trying to figure out whether that FET can handle enough current for your project? AN11158 from NXP might help clarify some of the many parameters that you need to take into account that are often overlooked. The Safe operating area, for example, is an important one that often gets skipped and people just look at the best-case scenario marketing numbers on the front page of the datasheet: “The Safe Operating Area (SOA) curves are some of the most important on the data sheet. The SOA curves show the voltage allowed, the current and time envelope of operation for the MOSFET. These values are for an initial Tmb of 25°C and a single current pulse. This is a complex subject which is further discussed in the appendix (Section 3.1).”
Understanding power MOSFET data sheet parameters - [Link]
Here is a simple programmable load. It’s basically a constant current sink that is controlled through a pot. The current is sunk through a high power FET which needs to be cooled to function properly – [via]
Here’s a link to a *really* simple linear constant current sink i put together
This design is about as simple as it gets. . .multi-turn pot controlled and readout done by a voltmeter:) The good news is that it works quite well for moderate loads. It was put together to regulate current flowing through a copper electroplating tank. Due to the monstrous Pentium II (or maybe III?) heat sink, it isn’t noticeably warm when eating 9A of current.
Simple analog programmable load - [Link]
Here is an interesting electronics gadget. It’s a semiconductor component tester that displays the type, pinout, and some relevant specifications of the device connected to its probes. [via]
It doesn’t matter how you connect the test clips to the component, the Atlas DCA can analyse a vast number of different component types including bipolar transistors, enhancement mode MOSFETs, depletion mode MOSFETs, Junction FETs (only gate pin identified), low power thyristors and triacs (less than 5mA trigger and hold), diodes, multiple diode networks, LEDs, bi-colour and tri-colour LEDs. It will even identify special component features such as diode protection and shunt resistors in transistors.
Semiconductor analyser determines part type and value - [Link]
Brookhaven physicist Ivan Bozovic wants to understand why a thin-film insulator transitions to the superconducting state. [via]
The resistance of superconductivity to rational explanation has prompted the U.S. Department of Energy’s (DoE) Brookhaven National Laboratory to fabricate atomically perfect ultra-thin-films capable of accurately characterize the transition from an insulator to superconductor. A normally insulating copper-oxide material (cuprate) was configured like the channel of a field-effect transistor (FET), using molecular beam epitaxy to create an atomically perfect superconducting film.
Lab aims for superconducting FET – [Link]
