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Posts by Andy aka‭

94 posts
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Q&A Relationship between bode plot and pole zero diagram

For any 2nd order low pass filter, the components (R, L and C for electrical and k, M and c for mechanical) can be reduced into two more meaningful quantities: - $\zeta$ (the damping ratio) $\omeg...

posted 4y ago by Andy aka‭  ·  edited 4y ago by Andy aka‭

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Q&A Pi-Filter for EMC

What would be the main considerations to use Pi-filters for EMC? Using the filter correctly and understanding its limitations EMC or EMI (electromagnetic interference) is noted for its high frequ...

posted 4y ago by Andy aka‭  ·  edited 4y ago by Andy aka‭

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Q&A Electrolytic capacitor lifetime rating

If you search through the electrolytic capacitor offerings from distributors like Farnell, RS, Digikey or Mouser, you find that the maximum life-time rating is commonly quoted as 5,000 or 10,000 ho...

1 answer  ·  posted 4y ago by Andy aka‭  ·  last activity 1y ago by Lorenzo Donati‭

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Q&A DC offset correction loop (DC servo loop). What's its advantage, compared to a high-pass RC filter?

What are the advantages of such DC offset removal loop, compared to an RC high-pass filter? The primary advantage is that it keeps the front-end amplifier output centred in its DC operating re...

posted 1y ago by Andy aka‭  ·  edited 1y ago by Andy aka‭

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Q&A Inductance vs frequency

Inductance is defined by the shape of the coil, the area of the coil, the number of turns in the coil, the distance between turns, the ferromagnetic permeability of material within (and surrounding...

posted 3y ago by Andy aka‭

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Q&A How to calculate the voltage of a coil?

The magnetic field will always be strongest in the middle of the solenoid. It will be slightly less at the ends of the solenoid and, it will be a lower value on the outside of the coil half way bet...

posted 2y ago by Andy aka‭

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Q&A Energy harvesting from non-invasive current sense transformer

Most of the energy produced by the CT windings is being wasted in the internal burden resistor. See this data sheet to see what I mean. I calculate that it has a 60 Ω burden resistor and, at full p...

posted 2y ago by Andy aka‭  ·  edited 2y ago by Andy aka‭

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Q&A Battery protection circuit

What kind of IC can be used to drive the MOSFET, so that when the voltage drops below 6.2 V the battery disconnects from the load? That reverse protection MOSFET works fine for reverse protect...

posted 2y ago by Andy aka‭  ·  edited 2y ago by Andy aka‭

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Q&A LED driver with feedback through light. Which feedback topology is better?

Which topology is preferable? The one below because the LED driver is less likely to produce instability and, if it does, you can always tweak C4 (upwards) in order to kill-off the potentially...

posted 8mo ago by Andy aka‭  ·  edited 8mo ago by Andy aka‭

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Q&A MAX485 transceivers breaking, Pi filter generating spikes?

What part of the absolute maximum ratings for the A and B data lines do you think would be protected by 33 volt TVS diodes: - If the chip is powered from a 5 volt supply then you use 5.6 volt TV...

posted 8mo ago by Andy aka‭

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Q&A MOSFET drain current ringing in saturation region

It's got nothing to do with the MOSFET's miller capacitance. Miller capacitance causes problems in common-source circuits but, your circuit is common-drain (or source follower) hence, with a steady...

posted 9mo ago by Andy aka‭  ·  edited 9mo ago by Andy aka‭

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Q&A Speed of EM waves from the point of view of an electrical engineer

A loss-less coaxial cable has inductance and capacitance and, their associated formulas introduce $\epsilon$ and $\mu$. But, to home-in on the velocity of propagation, the characteristic impedance ...

posted 11mo ago by Andy aka‭  ·  edited 11mo ago by Andy aka‭

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Q&A Transformer design for a Series Resonant Converter

The website that I mentioned before mentions the max flux density in ferrites at 400 kHz as being close to 0.04 T. Is this correct? No, you have misinterpreted the graph. The graph shown is fl...

posted 11mo ago by Andy aka‭  ·  edited 11mo ago by Andy aka‭

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Q&A Ceramic filter vs ceramic resonator

The Murata part you have chosen as a replacement is unsuitable. Its only application is to cheaply replace crystals in oscillators and, as such, it will have a profoundly tight bandwidth (maybe les...

posted 2y ago by Andy aka‭  ·  edited 2y ago by Andy aka‭

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Q&A Power amplifier for remote controller

The data sheet gives a perfectly good example of using the nRF24L01 without an external PA. It has an internal PA capable of driving an antenna <-- just look at the design example on page 63 wit...

posted 2y ago by Andy aka‭  ·  edited 2y ago by Andy aka‭

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Q&A Resistance of digital ampmeter

You might get lucky and be able to measure the input resistance using this method. It should work because the black socket (common) is shared by all measurements.

posted 3y ago by Andy aka‭

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Q&A Extract DC component of mixed signal

How can we extract a DC signal from a mixed signal? You use a low-pass filter with a cut-off frequency that is significantly lower than your lowest AC signal frequency. If you need better filt...

posted 3y ago by Andy aka‭

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Q&A Complementary transistor pairs - what is the point ?

To understand why complementary pairs are used, it's probably a good idea to think about the limitations of the NPN emitter-follower circuit: - It's a good circuit for delivering modest powers to ...

posted 4y ago by Andy aka‭  ·  edited 4y ago by Andy aka‭

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Meta Strange things happening

Why has my reputation dropped significantly over-night from around 352 to 316? Why are there a bunch of new people listed with decent reputations who seem to have appeared from nowhere?

0 answers  ·  posted 4y ago by Andy aka‭

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Q&A What benefit has a differential amplifier when measuring a sensor signal?

General cause of noise/interference The interference can be distant (such as lightning) or much closer (such as cables connecting "other" equipment) but, whatever the source, interference can be re...

posted 4y ago by Andy aka‭  ·  edited 4y ago by Andy aka‭

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Q&A Op-amp output error voltage

Input offset voltage $V_{OS}$ Your problem might be input offset voltage or $V_{OS}$. This can be several milli-volts and manifests as this modification to your original circuit (in red): - So, fo...

posted 4y ago by Andy aka‭  ·  edited 4y ago by Andy aka‭

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Q&A How do I design a boost converter? What are the basics I should know?

An on-line boost converter calculator Image from this website. The Operating Mode The circuit operates in either of two modes but, the voltage transfer equation is different for each mode. Therefo...

posted 4y ago by Andy aka‭  ·  edited 4y ago by Andy aka‭

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Q&A What reactance actually is?

"React" implies a response to an "event". For an inductor, the "event" is a change in current, $\frac{di}{dt}$ For a capacitor, the "event" is a change in voltage, $\frac{dv}{dt}$ $$$$ So, ...

posted 2y ago by Andy aka‭  ·  edited 2y ago by Andy aka‭

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Meta Apparent loss of reputation in last 24 hours

Has anyone else noticed a loss of reputation recently. I thought I checked yesterday and my reputation was a hundred points higher at 1889. Now it is at 1789. My vote summary doesn't indicate a los...

1 answer  ·  posted 1y ago by Andy aka‭  ·  last activity 1y ago by Monica Cellio‭

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Q&A What are some best practices for library management?

There is no definite answer to this but, if you want my advice, you store all symbols and footprints locally with your project. Of course you may begin by using standard parts from a global (comes-...

posted 1y ago by Andy aka‭  ·  edited 1y ago by Andy aka‭

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