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Beijing IP Court denies Innoscience’s appeal against EPC’s compensated-gate patent
Who needs DC-DC converters anyway.
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Why modulate a power amplifier?—and how to do it

We recently saw how certain audio power amplifiers can be used as oscillators. This Design Idea shows how those same parts can be used for simple amplitude modulation, which is trickier than it might seem.
Wow the engineering world with your unique design: Design Ideas Submission Guide
The relevant device is the TDA7052A, which we explored in some detail while making it oscillate. It has a so-called logarithmic gain-control input, the gain in dBs being roughly proportional to the voltage on that pin over a limited range.
However, we may want a reasonably linear response, which would mean undoing some of the chip designers’ careful work.
First question: why—what’s the application?
The original purpose of this circuit was to amplitude-modulate the power output stage of an infrasonic microphone. That gadget generated both the sub-10‑Hz baseband signal and an audio tone whose pitch varied linearly with it, allowing one to hear at least a proxy for the infrasonics. The idea was to keep the volume low during relatively inactive periods and only increase it during the peaks, whether those were positive or negative, so that frequency and amplitude modulation would work hand in hand.
The two basic options are to use the device’s inherent “log” law (more like antilog), so that the perceived loudness was modulated, or to feed the control pin with a logarithmically-squashed signal—the inverse of the gain-control curve—to linearize the modulation. The former is simpler but sounded rather aggressive; the latter, more complicated but smoother, so we’ll concentrate on that. The gain-control curve from the datasheet, overlaid with real-life measurements, is shown in Figure 1. Because we need gain to drive the speaker, we can only use the upper, more bendy, part of the curve, with around 26 dB of gain variation available.
Figure 1 The TDA7052A’s control voltage versus its gain, with the theoretical curve and practical readings.
For accurate linear performance, an LM13700 OTA configured as an amplitude modulator worked excellently, but needed a separate power output stage and at least ±6-V supplies rather than the single, split 5-V rail used for the rest of the circuitry. An OTA’s accuracy and even precision are not needed here; we just want the result to sound right, and can cut some corners. (The LM13700’s datasheet is full of interesting applications.)
Next question: how?
At the heart of this DI is an interesting form of full-wave rectifier. We’ll look at it in detail, and then pull it to pieces.
If we take a paralleled pair of current sources, one inverting and the other not, we can derive a current proportional to the absolute value of the input: see Figure 2.
Figure 2 A pair of current sources can make a novel full-wave rectifier.
The upper, inverting, section sources current towards ground when the input is positive (with respect to the half-rail point), and the lower, non-inverting part does so for negative half-cycles. R1 sets the transconductance for both stages. Thus, the output current is a function of the absolute value of the input voltage. It’s shown as driving R4 to produce a voltage with respect to 0 V, which sounds more useful than it really is.
Conventional full-wave rectifiers usually have a voltage output, stored on a capacitor, and representing the peak levels. This circuit can’t do that: connecting a capacitor across R4 merely averages the signal. To extract the peaks, another stage would be needed: pointless. By the way, the original thoughts for this stage were standard precision rectifiers with incorporated or added current sources, but they proved to be more complicated while performing no better—except for inputs below ~5 mV, where they had less “crossover distortion.”
The maximum output voltage swing is limited by the ratios of R4 to R2 (or R3). Excessive positive inputs will tend to saturate Q1, so VOUT can approach Vs/2. (The transistor’s emitter is servoed to Vs/2.) With R4 = R2 = R3, negative swings saturate Q2, but the ratio of R3 and R4 means that VOUT can only approach Vs/4. Q1 and Q2 respond differently to overloads, with Q2’s circuit folding back much sooner. If R2, R3, and R4 are all equal, the maximum unclipped voltage swing across R4 is just less than a quarter of the supply rail voltage.
Increasing R1 and making R4 much greater than R2 or R3 allows a greater swing for those negative inputs, but at the expense of increased offset errors. Adding an extra gain stage would give those same problems while needing more parts.
Applying the current source to the power amp
Conclusion: This circuit is great for sourcing a current to ground, but if you need a linear voltage output, it’s less useful. We don’t want linearity but something close to a logarithmic response, or the inverse of the power amp’s control voltage. Feeding the current through a network containing a diode can do just that, and the resulting circuit is shown in Figure 3.
Figure 3 Schematic of a power amplifier that is amplitude-modulated using the dual current source.
The current source is just as described above. With R1 = 100k, the output peaks at 23 µA for ±2.5 V inputs. That current feeds the network R4/R5/D3, which suitably squashes the signal, ready for buffering into A2’s Vcon input. The gain characteristic is now much more linear, as the waveforms in Figure 4 indicate. The TDA7052A’s Vcon pin normally either sinks or sources current, but emitter follower Q3 overrides that as well as buffering the output from the network.
Figure 4 Some waveforms from Figure 3, showing its operation.
To show the operation more cleanly, the plots were made using a 10-Hz tri-wave to modulate a 700-Hz sine wave. (The target application would have an infrasonic signal—from, say, 300 mHz to 10 Hz—modulating a pitch-linear audio tone ranging from about 250 to 1000 Hz depending on the signal’s absolute level.)
Some further notes on the circuitry
The values for R4/R5/D3 were optimized by a process of heuristic iteration, which is fancy-speak for lots of fiddling with trimmers until things looked right on the ’scope. These worked for me with the devices to hand. Others gave similar results; the absolute values are less important than the overall combination.
R7 and R8 may seem puzzling: there’s nothing like them on the PA’s datasheet. I found that applying a little bias to the audio input pin helps minimize the chip’s internal offsets, which otherwise cause some (distorted) feedthrough from the control voltage to the outputs. With a modulating input but no audio present, trim R7 for minimum signal at the output(s). The difference is barely audible, but it shows up clearly on a ’scope as traces that are badly slewed.
The audio feed needs to come from a volume-control pot. While it might seem more obvious to incorporate gain control in the network driving A2.4—after all, that’s the primary function of that pin—that proved over-complicated, and introduced yet more temperature effects.
Temperature effects! The current source is (largely) free of them, but D3, Q3, and A2 aren’t, and I have made no attempt to compensate for their contributions. The practical solution is to make R6 variable: a large, user-friendly knob labeled “Effect”, thus turning the problem into A Feature.
A2’s Vcon pin sinks/sources some (temperature-dependent) current, so varying R6 allows reasonable, if manual, temperature compensation. Because its setting affects both the gain and the part of the gain curve that we are using, the effective baseline is shifted, allowing more or less of the audio corresponding to low-level modulating signals to pass through. Figure 5 shows its effect on the output at around 20°C.
Figure 5 Varying R6 helps compensate for temperature problems and allows different audible effects.
Don’t confuse this circuit with a “proper” amplitude modulator! But for taking an audio signal, modulating it reasonably linearly, and driving the result directly into a speaker, it works well. The actual result can be seen in Figure 6, which shows both the detected infrasonic signal resulting from a gusty day and the audio output, whose frequency changes are invisible with the timebase used, but whose amplitude can be seen to track the modulating signal quite nicely.
Figure 6 A real-life infrasonic signal with the resulting audio modulated in both frequency (too fast to show up here) and amplitude.
—Nick Cornford built his first crystal set at 10, and since then has designed professional audio equipment, many datacomm products, and technical security kit. He has at last retired. Mostly. Sort of.
Related Content
- Power amplifiers that oscillate— Part 1: A simple start.
- Power amplifiers that oscillate—deliberately. Part 2: A crafty conclusion.
- Revealing the infrasonic underworld cheaply, Part 1
- Revealing the infrasonic underworld cheaply, Part 2
- Ultra-low distortion oscillator, part 1: how not to do it.
- Ultra-low distortion oscillator, part 2: the real deal
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Anritsu and AMD Showcase Electrical PCI Express Compliance up to 64 GT/s
Anritsu Corporation announced that it has helped AMD accelerate the testing of electrical compliance for PCI Express (PCIe) specification for pre-production AMD EPYC CPUs. Achieving a maximum data rate of 64 GT/s using the high-performance Anritsu BERT Signal Quality Analyzer-R MP1900A, testing was done under challenging backchannel conditions with insertion loss exceeding the specified 27 dB in the CEM specification, along with stress conditions applied using Spread Spectrum Clocking (SSC).
“In collaboration with Anritsu, we have achieved a stable demonstration of electrical compliance up to 64 GT/s,” said Amit Goel, corporate vice president, Server Engineering, AMD. “This early validation furthers our commitment to delivering reliable, high-speed I/O for future platforms powered by our next-generation AMD EPYCTM CPUs.”
“AMD is a key technology partner in advancing PCIe technology,” said Takeshi Shima, Director, Senior Vice President, Test & Measurement Company President of Anritsu Corporation. “We will continue to respond to various test needs and expand functions for PCIe compliance testing, while also contributing to quality evaluation and design efficiency of PCIe devices through proposals to standards organizations.”
PCIe 6.0 technology is the next-generation standard that provides a bandwidth of 64 GT/s per lane and up to 256 GB/s in a x16 configuration as a high-speed interface between internal devices such as CPUs, GPUs, SSDs, and network cards. While maintaining compatibility with previous standards, it achieves highly reliable and efficient communications in fields such as AI (Artificial Intelligence), HPC (High Performance Computing), and high-speed storage, greatly contributing to improving the performance of next-generation data centers and analytical systems.
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Half Adder PCB DIY
![]() | Me and my friend made this pcb that adds 2 bit with 2 bits and gives the result with 3 leds! It's the first pcb we design :) [link] [comments] |
Disassembling a LED-based light that’s not acting quite right…right?

A few months back, I came across an LED-based desk lamp queued up to go out to the trash. When I asked my wife about it, she said (or at least my recollection is that she said) that it had gone dim, so she’d replaced it with another one. But the device didn’t include any sort of “dimmer” functionality, and I wasn’t (at the time, at least) aware that LED lighting’s inherent intensity could fade over time, only that it would inevitably flat-out fail at some point.
My curiosity sufficiently piqued, especially since I’d intercepted it on the way to the landfill anyway, I decided to take it apart first. It’s Hampton Bay’s 15.5 in. Black Indoor LED Desk Lamp, originally sold by Home Depot and currently “out of stock” both in-store and online; I assume it’s no longer available for purchase. Here are some stock shots of what it looks like, to start:
See: no dimmer. Just a simple on/off toggle:
I don’t remember when we bought it or what we paid for it; it had previously resided on my wife’s sewing table. The Internet Archive has four “snapshots” of the page, ranging from the end of June 2020, when it was apparently on sale for $14.71 versus the $29.97 MSRP (I hope we snagged it then!), through early December of last year. My wife took up sewing during the COVID-19 lockdown, so a 2020-era acquisition sounds about right.
Here’s what it looks like in “action” (if you can call it that) in my furnace room, striving (and effectively failing) to differentiate its “augmentation” of the baseline overhead lighting:
Turn off the room light, and the lamp’s standalone luminary capabilities still aren’t impressive:
And here’s a close-up of the light source in “action”, if you can call it that, in my office:
Scan through the reviews on the product page and, unless I overlooked something, you won’t find anyone complaining that it’s not bright enough. Several of the positive reviews go so far as to specifically note that it’s very bright. And ironically, one of the (few) negative ones indicates that it’s too bright. The specs claim that it has a 3W output (no explicit lumens rating, however, far from a color temperature), which roughly translates to a 30W incandescent equivalent.
Time to dive in. Let’s begin with the underside, where a label is attached to a felt “foot”:
A Google search on “Arcadia AL40165” reveals nothing meaningful results-wise aside from the Home Depot product page. “Intertek 4000145” isn’t any more helpful. And, regardless of when we actually bought it, this particular unit was apparently manufactured in December 2016.
Peeling back the felt “foot”, I was initially confused by the three closed-end crimp connectors revealed underneath:
until I peeled it away the rest of the way and…oh yeah, the on/off switch:
Note the wiring colors. Typically, in my experience, the “+” DC feed corresponds to the white wire, with the “-“ return segment handled by the black wire, and the “+” portion of the circuit is what’s switched. This implementation seems opposite of that convention. Hold that thought.
Now for the light source. With the lamp switched off, you can see what appears to be a central LED surrounded by several others in circumference. Conceptually, this matches the arrangement I’ve seen before with LED light bulbs, so my initial working theory was that whatever circuitry was driving the LEDs in the perimeter had failed, leaving only the central one still operational. Why there would be such a two-stage arrangement at all wasn’t obvious, although I postulated that this same hardware might find use in another lamp with a three-position (bright/dim/off) toggle switch.
Removing the diffuser:
unfortunately dashed that theory; there was only a single LED in the center:
Here’s what it looks like illuminated, this time absent the diffuser:
A brief aside at this point: what’s with the second “right?” in the title? Well, when I mentioned to my wife the other day that I’d completed the teardown but hadn’t definitively figured out why the lamp had dimmed over time, she now said that to the best of her recollection, it had always been dim. Hmmm. If indeed I’d previously misunderstood her (and of course, my default stance is to always assume my wife is right…right?), then what we have is a faulty LED from the get-go. But just for grins, let’s pretend my dimmer-over-time recollection is correct and proceed.
One other root cause possibility is that the power supply feeding the LED is in the process of failing, thereby outputting under-spec voltage and/or current. Revisiting the earlier white-vs-black wire discussion, when I initially probed the solder connections with my multimeter using standard polarity conventions, I got a negative voltage reading:
The LED theoretically could have been operating in reverse-bias breakdown (albeit presumably not for long). But more likely, in conjunction with the earlier-mentioned switch location in the circuit, the wire colors were just reversed. Yep, that’s more like it:
Note that their connections to the LED might still be reversed, however. Or perhaps the lamp’s power supply was current output-compromised. To test both of these suppositions, I probe-connected and fueled the LED with my inexpensive-and-passable power supply instead:

With the connections using standard white vs. black conventions, I got…nothing. Reversed, the LED light output weakly matched that delivered when driven by the lamp’s own power supply. And my standalone power supply also informed me that the lamp pulls 180 mA at 10 V.
About that “lamp’s own power supply”, by the way (as-usual accompanied by a 0.75″/19.1 mm diameter U.S. penny for size comparison purposes):
The label refers to it as an “LED Driver,” but I’m guessing that it’s just a normal “wall wart”, absent a plug on the output end. And a Google search of “JG-LED1-5UPPL” (that’s the number 5, not an S, by the way) further bolsters that hypothesis (“Intertek 4002637” conversely wasn’t helpful at all, aside from suggesting that this power supply unit (PSU) was originally intended for a different lamp model). But I’m still baffled by the “DC5-10V MAX” notation in the labeled output specs…???
And removing two more screws, here’s what the plate the LED is mounted to looks like when separated from the “heatsink” behind it (note the trivial dab of thermal paste between them):
All leaving me with the same question I had at the start: what caused the LED-based desk lamp’s light output to dim, either over time or from the very beginning (depending on which spouse’s story you’re going with)? The most likely remaining culprit, I’m postulating, is the phosphor layer above the LED. I’ve already noted the scant-at-best heat-transfer interface between the LED and the metal plate behind it. More generally, as this device definitely exemplifies, my research suggests that inexpensive designs skimp on the number of LEDs to keep the BOM cost down, compensating by overdriving the one(s) that remain. The resulting thermal stress prematurely breaks down the phosphor, resulting in color temperature shifts and reduced light output, along with eventual complete component failure.
That’s my take; what’s yours? Let me know your thoughts in the comments!
—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.
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![]() | Before building a full temperature controlled chamber for slow /"natural" temp variance... I'm trying to see how my Scale behave in various environnements ahah [link] [comments] |
TrainingKit (3rd try)
![]() | im so proud making this :) [link] [comments] |
Top 10 TMT Bar in India
With India undergoing rapid urbanisation and infrastructural growth, there is a demand for materials that are either strong, resilient, or sustainable. These very TMT bars constitute the crux of modern construction. The city-based constructions in the country represent a host of varieties, such as residential, flyovers, industrial plants, skyscrapers, bridges, and buildings. The TMT bars warrant strength with a little flexibility so that its enhancement work on both durability and safety.
The whole range of TMT bars is competing to attract the buyers who seek high-performance bars with most advanced features. Raw materials, the technological process used for their manufacture, strength, ductility, and resistance to corrosion are among the differences existing among bars.
Here follows an all-encompassing guide for the Top 10 TMT Bar Brands in India, showing the feature-based distinction, application, and technology advantage.
- TATA Tiscon 550SD:
TATA Tiscon is the pioneer in the Indian TMT industry, being the first rebar brand in India. Supported by TATA Steel, it came out with the super ductile 550SD TMT bar using an advanced technology of Morgan, USA. TATA Tiscon 550SD bars, being GreenPro certified, hence are the environmentally friendly variety. With very high tensile strength and flexibility, they become an ideal candidate for earthquake-prone zones and heavy-duty infrastructure.
- SAIL’s SeQR:
Outstanding ductility is attributed to SAIL’s SeQR TMT bars that are manufactured by Steel Authority of India Limited, along with fire resistance and UTS/YS ratio. These bars are heat resistant up to the temperature of 600°C, and special corrosion-resistant varieties (HCR) are available for coastal or damp environments.
The TMT bars by SAIL possess excellent energy absorption that is desired for resisting the shocks from seismic or other sudden structural stresses.
- JSW Neosteel:
Produced from virgin iron ore, JSW Neosteel 500D/550D bars offer superior metallurgical quality. Because of their weldability and flexibility, they can resist seismic forces, making them sought after in regions prone to earthquakes.
Their low carbon content maintains structural integrity and allows easy fabrication, especially for large projects.
- Jindal Panther:
Jindal Panther TMT bars have ductility and bonding strength imparted by German TEMPCORE technology. Uniform rib patterns allow a better grip for concrete, which serves the objectives for high-rise buildings.
The FE 500D grade is said to embody the right mix of strength and flexibility.
- SRMB Steel:
The SRMB uses special X-pattern ribs to ensure better grip with cement and thereby minimize slippage and.mvare a better performance of the structure. These bars come with ISO and BIS certification, and therefore, they have good corrosion resistance and can be used for various residential and commercial applications.
- Kamdhenu TMT:
These micro-alloyed steel bars from Kamdhenu are ISI-certified and supplied all over India. They are classified as 550D TMT bars and have properties like good elongation, flexibility, and fire resistance.
They are a cost-effective option for home construction, real estate, and semi-urban projects.
- Vizag Steel:
Produced by the RINL- Rashtriya Ispat Nigam Limited, the Vizag Steel TMT bars find wide use in government and public infrastructure projects. Due to their uniform quality and corrosion-resistant properties, they are used for large-scale civil projects that include metros, flyovers, and industrial buildings.
- Shyam Steel:
Shyam Steel FE 500D TMT bars have advantages of fire resistance, corrosion protection, and elongation values and are ISO-certified with German technology. Such bars are recommended for high-rise residential complexes as well as commercial buildings.
- Electrosteel:
Electrosteel TMT bars, widely renowned for their bendability, low carbon content, and resistance to rust, give the buyers value for their money in terms of durability. Private contractors and small-scale builders looking for good value for money are going for these.
- Essar TMT Bars:
Essar TMT bars, processed by Thermex technology, ensure uniformity, weldability, and good finish; hence, they find widespread use in commercial buildings, real estate projects, and infrastructure and thus guarantee long durability.
Comparison:
Brand | Key Strengths | Grades | Technological Edge |
TATA Tiscon | GreenPro certified, super ductility, earthquake resistant | FE 415, FE 500, 550SD | Morgan USA tech, automated production |
SAIL SeQR | Fire-resistant up to 600°C, corrosion & seismic resistant | FE 500, EQR, HCR | High UTS/YS ratio |
JSW Neosteel | Made from virgin iron ore, high strength-to-weight ratio | 500D, 550D | Thermo-Mechanical Treatment, low carbon content |
Jindal Panther | German technology, ductile, strong bonding | FE 500D | TEMPCORE technology |
SRMB Steel | X-pattern ribs for superior grip, BIS & ISO certified | FE 500, 550 | X-rib technology, corrosion resistance |
Kamdhenu TMT | Micro-alloyed steel, pan-India reach | FE 500, 550D | ISI-certified |
Vizag Steel | Corrosion-resistant, government-preferred | FE 500D | Integrated steel plant production |
Shyam Steel | Weldability, fire resistance, high elongation | FE 500D | German machinery, ISO certified |
Electrosteel TMT | Rust-proof, strong bendability, BIS certified | FE 500D | Uniform heat treatment |
Essar TMT Bars | Excellent finish, good weldability, long life | FE 500D | Thermex process |
Choosing the right TMT bars is the cornerstone of structural integrity and durability into the future. Some factors are considered when choosing a TMT bar:
Grade of the Bar:
FE 415 is suitable for small residential buildings. FE 500 and 550D are used for high-rises, bridges, and commercial structures because of their higher tensile strength.
Corrosion Resistance:
Bars such as SAIL SeQR HCR or JSW Neosteel can be used for corrosion resistance in the coastal or humid environment.
Earthquake Resistance:
In seismic zones, bars with high ductility and UTS/YS ratio are required, such as Tata Tiscon 550SD or Jindal Panther.
Certifications & Quality Assurance:
Look for brands certified by BIS, ISO, or GreenPro, which assures compliance with Indian construction standards.
Conclusion:
India’s future infrastructure will rely on materials that combine strength and safety with sustainability. The right choice of TMT bar brand is therefore important for structural integrity. Whether it be for a small house or a mega commercial complex, the above-mentioned brands provide features suitable for a whole range of applications.
The post Top 10 TMT Bar in India appeared first on ELE Times.
Photon Design’s HAROLD quantum dot laser simulator available as a release candidate for customer evaluation
Cornell’s Tian selected for DARPA Director’s Fellowship award
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