by Roy McCammon:
The traditional three op-amp differential amplifier’s signal to noise ratio can be improved by 6dB by adding a resistor and slightly changing the connections. There is a trade-off though: The traditional topology has a high input impedance, whereas the low-noise version has a lower input impedance.
Differential amp has 6dB lower noise, twice the bandwidth - [Link]
Nich Fugalfrom @ Makeatronics is working on a BLDC motor controller.
Icall it a smart BLDC commutator. In a nutshell it’s a dedicated atmega328 that monitors the hall effect sensors on a brushless DC motor and takes care of the commutating and driver circuitry.
It’s smart because it has the ability to extract and keep track of motor position while monitoring the hall sensors. There’s also an option to plug in a quadrature encoder for higher resolution. The position can be sampled via a sample and hold input and communicated to a host controller via SPI.
I designed it to be an easy to use black box for interfacing with BLDC motors. All the host controller has to do is feed it direction (high/low) and PWM and the rest is done for you.
BLDC motor control using Atmega328 - [Link]
Design your PCB involving QFN or DQFN packages with this App note from Microchip.
Successful implementation of QFN and DQFN packages requires special consideration for printed circuit board (PCB) layout and solderpaste stencil production. This application note describes the important items to consider.
QFN packages are physically robust, thermally efficient, and occupy much less PCB space than equivalent QFP packages. They generally have superior lead inductance characteristics. They also present some particular design constraints. QFN packages generally have a row (QFN) or two (DQFN) of perimeter pads (“pads”) around a larger central pad (“flag” or “Epad”) encapsulated in a plastic body. These packages are surface-mounted to the target system PCB by a solder reflow process.
App note: PCB Design Guidelines for QFN and DQFN Packages - [Link]
The LTC®3114-1 is a versatile, wide operating voltage range synchronous monolithic buck-boost DC/DC converter with programmable average output current. The LTC3114-1’s proprietary buck-boost PWM control circuitry delivers low noise operation across the entire operating voltage range. Current mode control ensures exceptional line and load transient responses.
LTC3114-1 – 40V, 1A Synchronous Buck-Boost DC/DC Converter with Programmable Output Current - [Link]
The LTC2338 fully differential 1Msps SAR ADC family offers a wide ±10.24V true bipolar input range for high voltage industrial applications. The proprietary internal reference buffer maintains less than 1LSB error during sudden bursts of conversions, enabling true one-shot operation after lengthy idle periods. The internal reference can be overdriven to interface to a range of signal levels that swing above and below ground. The LTC2338 family eliminates complicated circuitry required to interface true bipolar signals to ADCs, and provides a compact solution for easy interfacing to 1.8V to 5V serial logic. The LTC2328 offers similar performance with a pseudo-differential input.
LTC2338-18 – 18-Bit, 1Msps, ±10.24V True Bipolar, Fully Differential Input ADC with 100dB SNR - [Link]
This device is a receiver circuit for a Digital Remote Thermometer. The thermometer operates by converting the sensor’s output voltage, which is calibrated and proportional to the measured temperature, to output cycles. The output cycles are transmitted in the supply cables and the receiver section counts the cycles from the transmitter; the calibrated counting are then displayed in the 7-segment LED displays.
The receiver circuit uses the 4093 Quad two input Schmitt NAND Gate IC as one of the logic components. Another component used is the 74HCT4520 dual 4-bit synchronous binary counter which is a high-speed Si-gate CMOS device. It has a dual 4-bit internally synchronous binary counters with an active high clock input and an active low clock input and buffered outputs. In this circuit, only two output levels from each of the binary counters, are utilized and the rest are connected to ground. The 74HCT4520 is coupled to the 74HCT4017 5‑stage Johnson decade counter for synchronized clocking. The MC14553B 3-digit BCD counter is also used in this circuit. The MC14553B consists of three negative edge triggered BCD Counters that are cascaded synchronously. In this circuit, the MC14553B controls the most significant (leftmost) value of the thermometer display. Lastly, the HEF4511B BCD to 7-segment BCD decoder is coupled to the MC14553BCP 7-segment displays. The HEF4511B decoder controls each of the displays to indicate the calibrated temperature.
The circuit is ideal for room temperature measurement. It displays the temperature in centigrade within the range of 00.0 to 99.9 degrees centigrade. Adjustments in the circuit are necessary to change the temperature ranges that can be accommodated by the circuit. Read the rest of this entry »
What’s inside a $13K Agilent Source Measure Unit capable of 15fA and 100nV resolution?
EEVblog #607 – Agilent B2912A Source Measure Unit SMU Teardown - [Link]
by Kalle Hyvönen:
Every once in a while I’d have needed a function generator but since I didn’t have one I always had to resort to some sort of quick and poor 555 kludge or something similar. I spotted a nice looking DDS (Direct Digital Synthesis) kit meant for the Juma RX-1 receiver that uses the AD9833 DDS chip. I figured I should be able to use it as a function generator because the frequency range looked pretty nice (0-8MHz in 10Hz, 100Hz, 1kHz or 100kHz steps) for my needs.
I ordered and built the kit and got it running easily, next thing I had to do was to design and build an output amplifier for the DDS board because the output was just around 250mV peak-to-peak. I wanted around 5V peak-to-peak (p-p) out so for the first revision I just built a simple non-inverting op-amp amplifier with an AD847 op-amp and +-5V supplies and a gain of 25. The +-5V supplies were generated with a 78L05 regulator and a ICL7660 charge pump from a single supply. It did not work too well because the opamp was too slow for a gain of 25, so I got massive attenuation at higher frequencies.
DDS Function Generator - [Link]
(Phys.org) —A device created by UCLA researchers could lead to a significant leap in the quality of images on smartphones, computer displays, TVs and inkjet printers.
The new material, and a new manufacturing process developed at UCLA, are used to produce semiconductors that are essential to liquid crystal displays and organic light-emitting diode, or OLED, displays.
Led by Yang Yang, the Carol and Lawrence E. Tannas Jr. Professor of Engineering at the UCLA Henry Samueli School of Engineering and Applied Science, the team created a high-performance device that can be produced without requiring a clean room or the expensive equipment now commonly in use.
Device could boost image quality for phones, computers and TVs - [Link]
A group of Korean researchers have turned their focus on supplying a reliable, efficient power source for wearables. Professor Byung Jin Cho of the Korea Advanced Institute of Science and Technology (KAIST) and his team, recognizing that supplying power that is stable and reliable is critical to the successful commercialization of wearables, have come up with a wearable power band that made technology news this week. The team noted that a flexible thermoelectric (TE) power generator would be the way to go to realize a wearable self-powered mobile device. They developed a wearable band-shaped item that produces electricity from the heat of the human body, The device size is 10 cm x 10 cm. Wearable electronics must be light, flexible, and equipped with a power source, which could be a portable, long-lasting battery or no battery at all but a generator, according to a KAIST release on Thursday, providing details about their work.
Power arm band for wearables harvests body heat - [Link]