High efficiency 4V supply QRP amplifier

Low voltage, high efficiency QRP RF amplifier project @ circuitsalad.com This is an example of a high efficiency QRP transmitter designed to work at very low supply voltages (3v-5v). It can produce 2 watts a 4 volt supply @ 70% efficiency. It uses small, inexpensive switching mosfets. The primary requirement for these mosfets is low […]

App note: Bipolar transistors maximum ratings

Deep dive on to the maximum ratings of bipolar transistors presented in this app note from Toshiba. Link here PDF! For transistors, the maximum allowable current, voltage, power dissipation and other parameters are specified as maximum ratings. The absolute maximum ratings are the highest values that must not be exceeded during operation even instantaneously. When […]

App note: Comparison of SiC MOSFET and Si IGBT

App note from Toshiba on the advantages of Silicon carbide (SiC) MOSFET over silicon (Si) IGBT. Link here PDF! Silicon carbide (SiC) comprises silicon (Si) and carbon (C) atoms. Each atom is surrounded by four different atoms in the form of a regular tetrahedron. SiC is a compound semiconductor with the densest tetrahedral arrangement. SiC […]

Cloning the ET-3404 6809 adapter for the Heathkit ET-3400

Dr. Scott Baker made the ET-3404 6809 adapter clone: I’ve become somewhat of a Heathkit ET-3400 enthusiast lately, after building my ETA-3400 memory/io clone. I decided to also clone the ET-3404, which is a 6809 adapter board for the ET-3400. Why? Simply for completeness sake. The official “experiments” for the ET-3404 aren’t all that exciting, […]

Laser cut project plate

Layne designed a laser-cut project plate: When I build electronics prototypes, it’s sometimes difficult to keep all the parts together without falling apart, especially if you need to move everything from one location to another. Between the breadboards, Arduino boards, programmers, FTDI cables, spare wires, and spare parts, I wanted to create a way to […]

Building a chaotic oscillator from common components

Tim blogged about his chaotic oscillator build: A chaotic oscillator is an electronic circuit that can exhibit “chaotic“, nonperiodic behavior. A commonly cited example is Chua’s circuit, but there are many others. I always regarded these as carefully designed, rather academic, examples. So I was a bit surprised to observe apparently chaotic behavior in a […]

App note: Load switches for mobile and computing applications

App note from Nexperia presenting simple load switches in mobile and computing applications. Link here (PDF) There are several reasons why a circuit or subsystem is required to be disconnected from the power supply using a load switch. A very simple and very common reason is that it helps saving power. An unpowered subsystem can […]

App note: Driving solenoids in automotive applications

App note from Nexperia about various solenoid driver used in automotive. Link here (PDF) There are a wide variety of solenoid drive circuit topologies. Most of them use MOSFETs in various configurations and driving modes. In this application note four of them will be discussed: solenoid driver with free-wheeling diode, solenoid driver with MOSFET avalanching, […]

App note: Power Battery Charger Calibration Fixture

Automated battery charger calibration fixture using Holtek’s ASSP MCUs. Link here (PDF) Power chargers for electric bicycles, electric motorcycles and power tools, etc., are all calibrated before delivery, thereby correcting any charging parameter drifts due to external component tolerances. This will ensure the output voltage and current conform to their specifications. However, traditional applications are […]

App note: BA45F55xx with power line transceiver

App note from Holtek on power line transceiver found on their BA45F55xx MCU. Link here (PDF) A Power Line Transceiver is a fire protection dual-line bus which is used as a data transceiver. The master gives a command to the slave using a voltage signal modulation method while the slave responds to the master using […]

App note: Op amps for MEMS Microphone preamp circuits

App note from TDK on design considerations of preamps used on MEMS microphones. Link here A microphone preamp circuit is used to amplify a microphone’s output signal to match the input level of the devices following it in the signal chain. Matching the peaks of the microphone’s signal level to the full-scale input voltage of […]

App note: Analog and digital MEMS microphone design considerations

App note from TDK about the things to consider when integrating analog and digital MEMS microphones into a system design. Link here (PDF) Microphones are transducers that convert acoustic pressure waves to electrical signals. Sensors have become more integrated with other components in the audio signal chain, and MEMS technology is enabling microphones to be […]

A sensitive, frequency-modulated dip meter capable of measuring resonator Q

Qrp Gaijin’s version of a dip meter to measure resonator Q: A highly-sensitive, narrow-band frequency-modulated dip meter offers a simple way to measure resonator Q. I have been working with an unusual dip meter circuit recently that has some interesting properties. The dip meter, also called a grid dip meter, is a simple homebrew instrument […]

Reverse engineering RAM storage in early Texas Instruments calculator chips

Reverse engineering RAM storage in early Texas Instruments calculator chips: Texas Instruments introduced the first commercial single-chip computer in 1974, combining the CPU, RAM, ROM, and I/O into one chip. This family of 4-bit processors was called the TMS1000. A 4-bit processor now seems very limited, but it was a good match for calculators, where […]