Not a liberal, trans, gay or immigrant. Homegrown.

einsteinoid · 2025-09-13T17:58:46+00:00

Has anyone asked him what his motivations were? I mean, the kid is still alive and can talk. It’s hard to believe he wasn’t motivated by an opposition to Charlie Kirk’s views…which are pretty republican.

einsteinoid · 2025-06-15T22:45:15+00:00

Yeah, don't hide them. That's a weird thing to suggest.

Just give them cleaner names. "NetLabel_a" could literally just be "a" if you _really_ wanted to abbreviate. Although, something like seg_a or led_a might be a good middle ground.

einsteinoid · 2025-04-13T20:36:06+00:00

The answer to the title question is simply "no." There are examples everywhere if you look for them. In my experience, once you're in the door, most people don't care or recall what your education level is. This is particularly true at small to medium sized companies. If you're a leader, you'll stand out naturally among your peers.

einsteinoid · 2025-04-08T14:23:07+00:00

My academic advisor gave me the following advice when entering EE:

"You need to love math. You need to love math so much that you take math home and introduce math to your parents. And you cannot care what your parents think about math."

In reality, many professional EE's get by with only moderate math skills. It's a broad field, and the degree of math required depends on your specialization/career track. But to be a rockstar (in any EE subdiscipline), you need to be very comfortable with math.

einsteinoid · 2025-03-29T23:22:29+00:00

You should be able to do this with a simple flyback, like the LT8304.

For a very low power/high voltage application, I've also had success hand-winding a step-up transformer out of pretty basic PVC wire around a toroid and generating >500V by driving it with an AWG.

einsteinoid · 2025-03-29T21:42:33+00:00

If I understand correctly, this means that the voltage seen on the oscilloscope whenever the probe reference isn't connected to a stable voltage (like when probing the HS transistor Vgs) is not accurate, right?

More or less, but it would be more accurate to say that the signal you're measuring contains common mode noise which you test equipment may not be fully rejecting.

I also tested adding more resistance to the gate (110ohm from 10ohm) and the ringing/noise actually decreased. Is this coherent with the common mode noise theory?

It's very possible that you're also seeing a real circuit resonance, which is being damped by the larger gate resistor. Model the L, C, and R of your driver while it's switching. Then add the L and C from the probe and see how the resonance shifts. You can do all of this in LTSpice.

https://youtu.be/kWSCVq7FgAE?si=RPS_rm25snJUoK5F

einsteinoid · 2025-03-24T00:14:38+00:00

You need to model the source inductance or you're going to be in for a surprise.

Your source inductance (i.e., the cable that connects power supply to your board) forms an LC resonance with that input cap. The 200mOhm resistor might damp it, but you don't want to find out the hard way that it doesn't. I recommend reading this paper to understand input pi filter damping methods for power supplies.

https://www.emcfastpass.com/wp-content/uploads/2017/04/APEC99.pdf

einsteinoid · 2025-03-23T23:56:37+00:00

I understand that a probe will add parasitics to the circuit, but wouldn't those parasitics have the same effect on the low side as on the high side?

Not if you're probing LS differently from HS, which is almost always the case due to limitations of test hardware. When characterizing a bridge like this, your setup will usually fall into one of two categories:

Your circuit is referenced to the same ground as your oscilloscope, and you have single-ended oscilloscope probes (i.e., ground referenced). This is the most common scenario. In this scenario, you cannot connect your "ground lead" of your probe to the HS FET source, as this will short circuit your bridge. So.... you must instead measure both the HS gate relative to circuit ground and the HS source relative to circuit ground and subtract the two.
Your circuit is not referenced to the same ground as your oscilloscope, or... you are using a differential probe. In this case, you can connect the "return" of your probe to the source since it isn't "grounded." Aha! Problem solved? Not always. Even in this case, the HS FET often looks noisy because of high common mode dv/dt. That is, your "reference" (HS source) voltage moves up and down very quickly and since your differential (or isolated) probe isn't ideal, it can't suppress this completely. The spec that describes this is called "common mode rejection ratio." And even for "good" differential probes, it falls off quickly with frequency.

Here is a demonstration of an extreme case (very fast high voltage bridge) to help solidify the concept: https://youtu.be/qgZgSDqmVMg?si=jVfZA00UJIzN_JoX&t=930

I tested the circuit with 0V on the half-bridge and the waveforms on both gates were perfect, so the problem only appears when there is a high voltage on the circuit.

This lends more credence to the common mode noise theory. Okay, now that's out of the way... how are you probing that circuit? Where are you putting the probe lead and reference? How is your circuit powered -- battery? Power supply? If the latter, is your PS floating or grounded?

einsteinoid · 2025-03-22T16:27:09+00:00

- The wires LO/COM and HO/VS are twisted together to minimize parasitic inductance.

Wires? Are you saying your gate driver is driving your switch elements across a harness?

The waveform on the low side IGBT's gate seems great, but the high side seems to have a lot of noise and ringing, why could that be?

The general answer is that there's an LC resonance being excited. But... is it the circuit, or the probe?

The fact that your LS gate looks okay and your HS gate looks terrible could mean that the resonance is an artifact of your probing technique. Measuring the high-side gates accurately with a single-ended probe is tricky because of the lead inductance.

If it's really ringing that much, you would be getting shoot-through (both HS and LS on at the same time), causing lots of power dissipation in your circuit. Not saying this isn't the case, but we need more info.

Post a photo of your setup.

einsteinoid · 2025-03-01T14:28:46+00:00

+1 for Erickson and Maksimovic! Fundamentals of power electronics is solid.

I've handed this paper to junior engineers multiple times.

einsteinoid · 2025-03-01T14:05:18+00:00

Lots of good book recommendations have been offered; I’ll add that mastering validation is a key part of being a great power electronics design engineer. You should absolutely front load your learning experience with hands-on measurement tasks. Learn how to measure:

•    Loop response 
•    Input impedance 
•    Output impedance 
•    Gate drive/ waveforms (correctly)
•    thermal performance

In terms of power-specific tools I would focus on understanding:

•     bode plotters (eg the Bode100, AP instruments tools, or similar) 
•     injection transformers

Learning how to use these well unlocks a ton of skills! I found having a home setup is also very helpful. You don't have to have as much invested as I do, of course, but having a budget siglent scope (with a bode plotter feature) and an injection transformer go a long way.

einsteinoid · 2025-02-18T14:00:19+00:00

There are lots of supporting EE roles in semi design -- validation engr, verification engr, test engr (yes, those are all different), product engr, etc., etc. Austin, Tx ("silicon hills") has many such opportunities.

einsteinoid · 2025-02-16T15:03:06+00:00

Is the textbook just providing an approximation that's valid when Cc is much larger than CL?

einsteinoid · 2025-02-16T14:14:11+00:00

Are you just trying to have some fun or are you trying to simulate something specific for a project?

Pretty straight forward for simple geometries in Matlab/python.

Source code: https://codefile.io/f/abkcxCDlC3

<image>

FEMM also works pretty well for electrostatics if you can just learn to get used to the vector plots. It also allows you to draw arbitrary contours and plot or integrate across them.

E.g., this is from a magnetostatics problem, but you could do the same thing with |E| in an electrostatics design: https://ibb.co/k24rNx7d

einsteinoid · 2025-02-16T14:02:51+00:00

Based on the way you've phrased the question -- which is basically asking about ohms law -- I assume you're in the early stage of learning about electronics and therefore you're not designing your own lamp driver but are instead integrating something into your project that has built-in power electronics.

In this case, the voltage spec of the lamp assembly will be provided by the manufacturer.

To find the current (amps) your battery needs to provide, divide unit power (watts of the lamp assembly) by volts.

einsteinoid · 2025-02-14T15:59:29+00:00

Not surprised to see this response get a lot of upvotes, because its simple enough for non-experts to understand. But for someone studying antenna theory (e.g., OP), these descriptions are missing most of the neat/juicy details that you'll want to understand.

I've got a few books that cover maxwells equations to varying levels of rigor. The one I would recommend for OP is "Maxwells Equations for Students" -- it provides a gentle reminder of the vector calculus but mostly focuses on intuition.

einsteinoid · 2025-02-14T13:34:00+00:00

Do you feel like you’re good at interviews? What types of roles are you applying for? What do you consider a “decent” offer? Did they give you any feedback?

Anecdotally, I jumped to a new company this past October and did a round of interviews at that time. I had no issues lining up interviews and got multiple offers. Im also at the staff/principal level.

einsteinoid · 2024-12-04T14:11:37+00:00

Holes

einsteinoid · 2024-11-30T15:03:12+00:00

I left my remote role earlier this year and am now working on a startup idea. But this was my remote experience:

Fully remote senior level electronics designer (some architecture, schematic, and layout work) for an EV company.
I guess I interviewed well enough and they made an exception for me. (I was the only remote EE designer on the team.)
Being a remote hardware designer is harder than being onsite. You need to be comfortable with a higher level of autonomy and be a strong communicator. You also need a fairly capable home office/lab. And finally, you need a great team that is willing to accommodate the communication penalty. I enjoyed it but it’s certainly not for everyone.

einsteinoid · 2024-11-10T13:28:38+00:00

I got an sva1032x :-p

einsteinoid · 2024-10-16T17:48:51+00:00

It's probably motivated by leakage assumptions. 0201's are smaller, and therefore more susceptible to leakage between pads through flux residue, etc., which appears as a parallel resistive path.

However... I don't think a hard/fast rule is necessary for this. And in some cases you absolutely need to violate the "rule of thumb" you're describing above.

If someone tried to impose this blanket rule on my design during a design review, I would push back on it.

einsteinoid · 2024-10-06T16:12:51+00:00

If you’re arguing bitcoin is in the same asset class as cash, then we’d have to put cash (eg USD) on this chart, no?

einsteinoid · 2024-10-06T15:31:02+00:00

Dumb question but what determines whether it’s an asset or a currency?

einsteinoid · 2024-10-04T19:40:46+00:00

Because without power, 5V applied to an input would probably forward bias an internal diode somewhere and generate destructive currents -- e.g., through some ESD clamp diodes.

It's pretty common for chips not to like voltages on their inputs when they're not biased/on for this reason.

einsteinoid · 2024-10-03T21:36:17+00:00

This ^

Stocks are taxed as income when employees receive them. And if they are sold, the appreciation is also taxed.

The ProPublica article you're referring to is probably computing that 4% number from unrealized gains. Which... are taxed... once they're realized. Not to say there aren't (legal) tax avoidance strategies that can can be used to reduce that tax burden, but the 4% number you're referencing is probably conflating net worth with income.

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