New electronic phenomenon discovered

Physics researchers at the University of North Florida's Atomic LEGO Lab discovered a new electronic phenomenon they call 'asymmetric ferroelectricity'. The research demonstrated this phenomenon for the first time in engineered two-dimensional crystals.

New technology will allow important metals to be made more efficiently

Researchers have invented a cheaper, safer, and simpler technology that will allow a 'stubborn' group of metals, such as the Pt-group elements, to be transformed into thin films for various practical applications.

All in your head: Exploring human-body communications with binaural hearing aids

Wearable technology seems all poised to take over next-generation electronics, yet most wireless communication techniques are not up to the task. To tackle this issue, scientists have delved deep into human-body communications, in which human tissue is used as the transmission medium for electromagnetic signals. Their findings pave the way to more efficient and safer head-worn devices, such as binaural hearing aids and earphones.

Brain-inspired highly scalable neuromorphic hardware

Researchers fabricated a brain-inspired highly scalable neuromorphic hardware by co-integrating single transistor neurons and synapses. Using standard silicon complementary metal-oxide-semiconductor (CMOS) technology, the neuromorphic hardware is expected to reduce chip cost and simplify fabrication procedures.

Mixing a cocktail of topology and magnetism for future electronics

A new review throws the spotlight on heterostructures of topological insulators and magnetic materials, where the interplay of magnetism and topology can give rise to exotic quantum phenomena that are promising building blocks for future low-power electronics. Provided suitable candidate materials are found, a 'cocktail' of topological physics and magnetism could produce these key states at room temperature and without any magnetic field, making them a viable ultra-low energy alternative to current, CMOS electronics.

Kick-starting supersonic waves in antiferromagnets

Researchers have demonstrated a new technique to generate magnetic waves in antiferromagnets that propagate through the material at a speed much larger than the speed of sound. These so-called spin waves produce a lot less heat than conventional electric currents, making them promising candidates for future electronic devices with significantly reduced power consumption.

MOSFET Gate Resistor

Do you need a MOSFET gate resistor? What value should it be? And should it go before or after the pulldown resistor?

If you’re a bit impatient and just want the answer, here it is: You most likely need a gate resistor. And 1000 Ω will most likely work. See the circuit diagram below for connecting your MOSFET gate resistor (the Pull-down resistor is optional):

Why Do You Need a Gate Resistor?

In how transistors work, we briefly touched upon that gate-to-source of a MOSFET acts as a capacitor.

And a capacitor works like this:

• When a capacitor is charging – current flows through it. A lot in the beginning, then less and less.
• When a capacitor is fully charged – no current flows through it.

When your MOSFET is turned on, its gate-source capacitor is fully charged. So there is no current flowing through the gate.

But when your MOSFET is being turned on, you’ll have a current that is charging this gate-source capacitor. So for a small fraction of a second, there can be a lot of current flowing.

To make sure this short burst of current isn’t too high for your Arduino/Raspberry Pi/microcontroller (or whatever you’ve connected it to) you need to add a resistor in series between the output pin and the MOSFET transistor’s gate:

Choosing A Resistor Value

Often 1000 Ω is a good enough value for this. But it depends on your circuit.

You can calculate the maximum current you get from a resistor by using Ohm’s law for current:

For example in the case of Arduino that has 5V on its output pins, 1000 Ω gives you a maximum current of 5 mA (and Arduino pins can handle up to 40 mA):

Keep in mind that the higher resistance you are using, the slower the MOSFET will turn on.

MOSFET Gate Resistor Placement

Are you using a pulldown resistor for your MOSFET? Then remember that if the gate resistor is placed to the left of the pulldown resistor, you get a voltage divider circuit that will reduce the voltage to the gate:

If you have chosen a gate resistor that is at least 100 times smaller than the pulldown resistor, then the reduction in voltage is so small that it doesn’t matter. But if they are a bit closer in value, the voltage on your gate will be lower than the pin voltage.

The solution? Switch places between the two so that the pulldown resistor is connected directly to the output pin:

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