National is celebrating their 50th birthday. Congratulations!
Archive for May, 2009
If you’re like us, you work on a laptop and bring it to meetings to check the latest analog news (a.k.a. surf) while the managers drone. HP recently recalled 70,000 laptop batteries and now they’re recalling more! To be on the safe side don’t use your laptop as a, well, laptop.
Hewlett-Packard Co, the world’s largest PC maker, is recalling 15,000 laptop batteries distributed in China because of a danger they could overheat, China said on Tuesday on its quality inspections web site. More here.
Also reminds us to look for features like overvoltage and thermal protection while designing the battery charging system for portable products. Don’t want to get in HP’s hot situation.
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MCP73113 Li-Ion/Li-Polymer Battery Charge Management Controller with OVP
New to Microchip’s Linear Product Line is a family of operational amplifiers optimized for high speed, low noise and distortion, single-supply operation with rail-to-rail output and an input that includes the negative rail.
Well then….what’s so special about mCal?
The internal mCal circuitry, when activated, starts a delay timer (to wait for the op amp to settle to its new bias point), then calibrates the input offset voltage (VOS). The mCal circuitry is triggered at power-up (and after some power brown out events) by the internal POR, and by the memory’s Parity Detector. The power up time, when the mCal circuitry triggers the calibration sequence, is 200 ms (typical).
What applications benefit from mCal?
The following are a few examples of applications that benefit from mCal and low offset performance.
POWER DRIVER WITH HIGH GAIN: The figure below shows a power driver with high gain (1 + R2/R1). The MCP651/2/5 op amp’s short circuit current makes it possible to drive significant loads. The calibrated input offset voltage supports accurate response at high gains. R3 should be small, and equal to R1||R2, in order to minimize the bias current induced offset.
OPTICAL DETECTOR AMPLIFIER: The figure below shows a transimpedance amplifier, using the MCP651 op amp, in a photo detector circuit. The photo detector is a capacitive current source. The op amp’s input common mode capacitance (5 pF, typical) acts in parallel with CD. RF provides enough gain to produce 10 mV at VOUT. CF stabilizes the gain and limits the transimpedance bandwidth to about 1.1 MHz. RF’s parasitic capacitance (e.g., 0.2 pF for a 0805 SMD) acts in parallel with CF.
More about this new product family: Click Here
More about Eval Boards that support this product family: Click Here
Fun little instructable will show you the basics of creating your own cheap and easy wireless power mat, which you can use to power your device through the air. Perhaps juice up the frequency and power and mod it into something more functional.
Inductive Coupling uses magnetic fields to transfer power. There is a primary coil, which generates a magnetic field. Then there is another secondary coil which is composed of a capacitor and a coil, the capacitor creates a resonant circuit with the primary and secondary coils. Instructable here.
Summer has come and with it the problem of dead devices. How so? Forgetfulness and, well, laziness. Here in Arizona, we’re already heating up to 100 degrees, being baked like an oven. Shuffling around one can generate thousands of volts, easily reaching 10 to 15 kV in our low humidity.
Although IC manufacturers provide a first line of defense with on-chip protection devices that can withstand ≥2-kV (human-body-model) ESD events, it’s best to control the static electricity in your environment. Grounded wrist straps, static-dissipative table tops, conductive heel straps, grounded floor mats, and ion generators are there to help. So before pulling those parts out of the bag or tube, don’t forget to strap on.
The auto-zero architecture is similar in concept to that of a chopper-stabilized amplifier in that there is a nulling amplifier and a main amplifier. However, significant improvements have been made over the years to minimize noise, charge injection and other performance issues associated with chopper-stabilized op amps. Various manufacturers use different terms to define this architecture, such as “auto-zero,” “autocorrelating zeroing” and “zero-drift.” Continued
The above exerpt is from the Portable Design article: Auto-Zero Op Amps: Inherent Benefits in Portable Signal-Conditioning Applications.
The auto-zero architecture continually self-corrects for the offset-voltage error of the amplifier. There’s some good information in the article and if you have an application requiring very low offset and drift, say a sensitive scale for your, uh, cooking spices then definitely click on the link and learn about Auto-Zero Op Amps and their beneficial attributes.
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