Українською
  In English
Feed aggregator
The second version of my A+E Key M.2 to Front Panel USB 2.0 Adapter Card
![]() | I posted V1.0 here a few months ago and a couple people pointed out some problems. I also found some of my own. I need to change the design, so I've made V1.1. I've made a lot of improvements to the board and my documentation. All of my progress can be tracked in the v1.1 branch on my github. I am planning on ordering new boards soon. Any feedback would be appreciated. [link] [comments] |
Flip ON Flop OFF: high(ish) voltages from the positive supply rail

We’ve seen lots of interesting conversations and Design Idea (DI) collaboration devising circuits for power switching using inexpensive (and cute!) momentary-contact SPST pushbuttons. A recent and interesting extension of this theme by frequent contributor R Jayapal addresses control of relatively high DC voltages: 48 volts in his chosen case.
Wow the engineering world with your unique design: Design Ideas Submission Guide
In the course of implementing its high voltage feature, Jayapal’s design switches the negative (Vss a.k.a. “ground”) rail of the incoming supply instead of the (more conventional) positive (Vdd) rail. Of course, there’s absolutely nothing physically wrong with this choice (certainly the electrons don’t know the difference!). But because it’s a bit unconventional, I worry that it might create possibilities for the unwary to make accidental, and potentially destructive, misconnections.
Figure 1’s circuit takes a different tack to avoid that.
Figure 1 Flip ON/Flop OFF referenced to the V+ rail. If V+ < 15v, then set R4 = 0 and omit C2 and Z1. Ensure that C2’s voltage rating is > (V+ – 15v) and if V+ > 80v, R4 > 4V+2
Figure 1 returns to an earlier theme of using a PFET to switch the positive rail for power control, and a pair of unbuffered CMOS inverters to create a toggling latch to control the FET. The basic circuit is described in “Flip ON Flop OFF without a Flip/Flop.”
What’s different here is that all circuit nodes are referenced to V+ instead of ground, and Zener Z1 is used to synthesize a local bias reference. Consequently, any V+ rail up to the limit of Q1’s Vds rating can be accommodated. Of course, if even that’s not good enough, higher rated FETs are available.
Be sure to tie the inputs of any unused U1 gates to V+.
Stephen Woodward’s relationship with EDN’s DI column goes back quite a long way. Over 100 submissions have been accepted since his first contribution back in 1974.
Related Content
- Flip ON flop OFF
- Flip ON Flop OFF for 48-VDC systems
- Flip ON Flop OFF without a Flip/Flop
- Elaborations of yet another Flip-On Flop-Off circuit
- Latching D-type CMOS power switch: A “Flip ON Flop OFF” alternative
The post Flip ON Flop OFF: high(ish) voltages from the positive supply rail appeared first on EDN.
Hack Club Highway - My first two PCBs
![]() | Project 1: µController - A Custom Game Controller for Unrailed submitted by /u/RunTheBot I designed this compact controller specifically for playing Unrailed. Here's what makes it special:
The journey wasn't without its challenges - I may have slightly overheated a Nano S3 during assembly 😅 but managed to salvage it with some creative bodge-wiring using a Xiao. Currently, it's fully functional except for one hall effect sensor! Project 2: The Overkill Macro PadEver thought "I need more buttons"? Well, how about 100 of them? Features: - 100 mechanical switches - Individual RGB LEDs for EVERY key - OLED display - Powered by a Raspberry Pi Pico - Auto polarity-correcting power input (because who has time to plug in power the right way?) Some fun challenges I ran into: - Had to redo the PCB multiple times (always double-check your footprints!) - Learned the hard way about thermal management during soldering - Discovered that 100 LEDs can create some interesting signal integrity challenges - Found some microscopic shorts that only showed up when the board heated up (freezer debugging FTW!) Currently, it's working with some bodge wires, though a few keys are still being stubborn. The case needs some tweaking, but hey, that's part of the fun of DIY, right? Lessons Learned
Both projects are open source, and I'll be happy to share more details if anyone's interested! Let me know if you have any questions! [link] [comments] |
k-Space hires new sales director
Top 10 Machine Learning Frameworks
Today’s world includes self-driving cars, voice assistants, recommendation engines, and even medical diagnoses thrive powered at their core by robust machine learning frameworks. Machine learning frameworks are the solution that really fuels all these intelligent systems. This article will delve into the definition and what it means to function as a machine learning framework, mention some popular examples, and review the top 10 ML frameworks.
A machine learning framework is a set of tools, libraries, and interfaces to assist developers and data scientists in building, training, testing, and deploying machine learning models.
It functions as a ready-made software toolkit, handling the intricate code and math so that users may concentrate on creating and testing algorithms.
Here is how most ML frameworks work:
- Data Input: You feed your data into the framework (structured/unstructured).
- Model Building: Pick or design an algorithm (e.g neural networks).
- Training: The model is fed data so it learns by adjusting weights via optimization techniques.
- Evaluation: Check the model’s accuracy against brand new data.
- Deployment: Roll out the trained model to implementation environments (mobile applications, website etc.)
Examples of Machine Learning Frameworks:
- TensorFlow
- PyTorch
- Scikit-learn
- Keras
- XGBoost
Top 10 Machine Learning Frameworks:
- TensorFlow
Google Brain created the open-source TensorFlow framework for artificial intelligence (AI) and machine learning (ML). It was created to make it easier to create, train and implement machine learning models especially deep learning models across several platforms by offering the necessary tools.
Applications supported by TensorFlow are diverse and include time series forecasting, reinforcement learning, computer vision and natural language processing.
- PyTorch
Created by Facebook AI Research, PyTorch is an eminent, yet beginner-friendly academic research framework. PyTorch uses dynamic computation graphs that provide easy debugging and testing. Being very flexible, it is mostly preferred while conducting deep learning work with a number of breakthroughs and research papers taking PyTorch as their primary framework.
- Scikit-learn
Scikit-learn is a Python library built upon NumPy and SciPy. It’s the best choice for classical machine learning algorithms like linear regression, decision trees, and clustering. It’s simple API with documented instructions for use makes it fit for handling small to medium-sized datasets when prototyping.
- Keras
Being a high-level API, Keras is tightly integrated into TensorFlow. More modern deep learning techniques promoted and supported from the interface deliver ease in realizing ML problems. Keras covers all the stages that an ML engineer goes through in the realization of a solution: data processing, hyperparameter tuning, deployment, etc. Its intention was to enable fast experimentation.
- XGBoost
XGBoost- Extreme Gradient Boosting-is an advanced machine-learning technique geared toward efficiency, speed, and utmost performance. It is a GBDT-based machine-learning library that is scalable and distributed. It is the best among the machine learning libraries for regression, classification, and ranking, offering parallel tree-boosting.
The understanding of the bases of machine learning and the methods on which XGBoost runs is important; these are supervised machine learning, decision trees, ensemble learning, and gradient boosting.
- LightGBM
LightGBM is an open-source high-performance framework and is also created by Microsoft. It is the technique on gradient boosting used in ensemble learning framework.
LightGBM is a fast gradient boosting framework that uses tree-based learning algorithms. It was developed in the product environment while keeping the requirements of speed and scalability in mind. Training times are much shorter, and the computer resources are fewer. Memory requirements are also less, making it suitable for resource-starved systems.
LightGBM will also, in many cases, provide better predictive accuracy because of its novel histogram-based algorithm and optimized decision tree growth strategies. It allows for parallel learning, distributed training on multiple machines, and GPU acceleration-to scale to massive datasets while maintaining performance
- Jax
JAX is an open-source machine learning framework based on the functional programming paradigm developed and maintained by Google. JAX stands for “Just Another XLA,” where XLA is short for Accelerated Linear Algebra. It is famous for numerical computation and automatic differentiation, which assist in the implementation of many machine learning algorithms. JAX, being a relatively new machine learning framework, is some way in providing features useful in realizing a machine learning model.
- CNTK
Microsoft Cognitive Toolkit (CNTK) is an open-source deep learning framework developed by Microsoft to implement efficient training of deep neural networks. It is scalable in training models across multiple GPUs and across multiple servers, especially good for large datasets and complex architectures. Weighing its flexibility, CNTK supports almost all classes of neural networks and is useful in many kinds of machine-learning tasks such as feedforward, convolutional, and recurrent networks.
- Apache Spark MLlib
Apache Spark MLlib is Apache Spark’s scalable machine learning library built to ease the development and deployment of machine learning apps for large datasets. It offers a rich set of tools and algorithms for various machine learning tasks. It is designed for simplicity, scalability and easy integration with other tools.
- Hugging Face Transformers
Hugging Face Transformers is an open-source framework specializing in deep learning paradigms developed by Hugging Face. It provides APIs and interfaces for the download of state-of-the-art pre-trained models. Following their download, the user can then fine-tune the model to best serve his or her purpose. The models perform usual tasks in all modalities, including natural language processing, computer vision, audio, and multi-modal. Hugging Face Transformers represent Machine Learning toolkits for NLP, trained on specific tasks.
Conclusion:
Machine learning frameworks represent the very backbone of modern AI applications. Whether a beginner or a seasoned pro building very advanced AI solutions, the right framework will make all the difference.
From huge players such as TensorFlow and PyTorch down to niche players such as Hugging Face and LightGBM, each framework claims certain virtues that it is best suited for in different kinds of tasks and industries.
The post Top 10 Machine Learning Frameworks appeared first on ELE Times.
Keysight Automated Test Solution Validates Fortinet’s SSL Deep Inspection Performance and Network Security Efficacy
Keysight BreakingPoint QuickTest simplifies application performance and security effectiveness assessments with predefined test configurations and self-stabilizing, goal-seeking algorithms
Keysight Technologies, Inc. announced that Fortinet chose the Keysight BreakingPoint QuickTest network application and security test tool to validate SSL deep packet inspection performance capabilities and security efficacy of its FortiGate 700G series next-generation firewall (NGFW). BreakingPoint QuickTest is Keysight’s turn-key performance and security validation solution with self-stabilizing, goal-seeking algorithms that quickly assess the performance and security efficacy of a variety of network infrastructures.
Enterprise networks and systems face a constant onslaught of cyber-attacks, including malware, vulnerabilities, and evasions. These attacks are taking a toll, as 67% of enterprises report suffering a breach in the past two years, while breach-related lawsuits have risen 500% in the last four years.
Fortinet developed the FortiGate 700G series NGFW to help protect enterprise edge and distributed enterprise networks from these ever-increasing cybersecurity threats, while continuing to process legitimate customer-driven traffic that is vital to their core business. The FortiGate 700G is powered by Fortinet’s proprietary Network Processor 7 (NP7), Security Processor 5 (SP5) ASIC, and FortiOS, Fortinet’s unified operating system. Requiring an application and security test solution that delivers real-world network traffic performance, relevant and reliable security assessment, repeatable results, and fast time-to-insight, Fortinet turned to Keysight’s BreakingPoint QuickTest network applications and security test tool.
Using BreakingPoint QuickTest, Fortinet validated the network performance and cybersecurity capabilities of the FortiGate 700G NGFW using:
- Simplified Test Setup and Execution: Pre-defined performance and security assessment suites, along with easy, click-to-configure network configuration, allow users to set up complex tests in minutes.
- Reduced Test Durations: Self-stabilizing, goal-seeking algorithms accelerate the test process and shorten the overall time-to-insight.
- Scalable HTTP and HTTPS Traffic Generation: Supports all RFC 9411 tests used by NetSecOPEN, an industry consortium that develops open standards for network security testing. This includes the 7.7 HTTPS throughput test, allowing Fortinet to quickly assess that the FortiGate 700G NGFW’s SSL Deep Inspection engine can support up to 14 Gbps of inspected HTTPS traffic.
- NetSecOPEN Security Efficacy Tests: BreakingPoint QuickTest supports the full suite of NetSecOPEN security efficacy tests, including malware, vulnerabilities, and evasions. This ensures the FortiGate 700G capabilities are validated with relevant, repeatable, and widely accepted industry standard test methodologies and content.
- Robust Reporting and Real-time Metrics: Live test feedback and clear, actionable reports showed that the FortiGate 700G successfully blocked 3,838 of the 3,930 malware samples, 1,708 of the 1,711 CVE threats, and stopped 100% of evasions, earning a grade “A” across all security tests.
Nirav Shah, Senior Vice President, Products and Solutions, Fortinet, said: “The FortiGate 700G series next-generation firewall combines cutting-edge artificial intelligence and machine learning with the port density and application throughput enterprises need, delivering comprehensive threat protection at any scale. Keysight’s intuitive BreakingPoint QuickTest application and security test tool made our validation process easy. It provided clear and definitive results that the FortiGate 700G series NGFW equips organizations with the performance and advanced network security capabilities required to stay ahead of current and emerging cyberthreats.”
Ram Periakaruppan, Vice President and General Manager, Keysight Network Test and Security Solutions, said: “The landscape of cyber threats is constantly evolving, so enterprises must be vigilant in adapting their network defenses, while also continuing to meet their business objectives. Keysight’s network application and security test solutions help alleviate the pressure these demands place on network equipment manufacturers by providing an easy-to-use package with pre-defined performance and security tests, innovative goal-seeking algorithms, and continuously updated benchmarking content, ensuring solutions meet rigorous industry requirements.”
The post Keysight Automated Test Solution Validates Fortinet’s SSL Deep Inspection Performance and Network Security Efficacy appeared first on ELE Times.
TIL you can use the iPhone magnifier app to inspect PCB much better than the camera app
![]() | One of the difficulties I had with the camera app is that you couldn't leave the LED on for close up pictures to read off resistor codes. The magnifier app will let you manually leave the iPhone flashlight on, and set a fixed zoom if needed and save the controls layout so you can jump back to PCB inspection. The first picture is with the magnifier and the second is with the iPhone camera app. It saves you from needing to take a PCB to a microscope to figure out what was up with it. Also saves some disassembly to get the PCB out of whatever it is installed in. I was able to figure out the board at some point had been hand soldered with the wrong resistor value and that was the source of all our issues. [link] [comments] |
First Ethernet-Based AI Memory Fabric System to Increase LLM Efficiency
AXT’s Q2 revenue constrained by slower-than-expected China export permitting
Vijay Varada's Braille display modified so that the driver of the display is integrated into the cell.
https://hackaday.io/project/191181-electromechanical-refreshable-braille-module Based on this.
This board has a cheap ch32v003 microcontroller and communicates by i2c and can be chained together so you can have multiple on the same i2c bus. This is the smallest board I have ever made. Feedback appreciated, Thank you!
[link] [comments]
The next AI frontier: AI inference for less than $0.002 per query

Inference is rapidly emerging as the next major frontier in artificial intelligence (AI). Historically, the AI development and deployment focus has been overwhelmingly on training with approximately 80% of compute resources dedicated to it and only 20% to inference.
That balance is shifting fast. Within the next two years, the ratio is expected to reverse to 80% of AI compute devoted to inference and just 20% to training. This transition is opening a massive market opportunity with staggering revenue potential.
Inference has a fundamentally different profile—it requires lower latency, greater energy efficiency, and predictable real-time responsiveness than training-optimized hardware, which entails excessive power consumption, underutilized compute, and inflated costs.
When deployed for inference, the training-optimized computing resources result in a cost-per-query at one or even two orders of magnitude higher than the benchmark of a cost of $0.002 per query established by a 2023 McKinsey analysis based on the Google 2022 search activity estimated to be in average 100,000 queries per second.
Today, the market is dominated by a single player whose quarterly results reflect its stronghold. While a competitor has made some inroads and is performing respectably, it has yet to gain meaningful market share.
One reason is architectural similarity; by taking a similar approach to the main player, rather than offering a differentiated, inference-optimized alternative, the competitor faces the same limitations. To lead in the inference era, a fundamentally new processor architecture is required. The most effective approach is to build dedicated, inference-optimized infrastructure, an architecture specifically tailored to the operational realities of processing generative AI models like large language models (LLMs).
This means rethinking everything from compute units and data movement to compiler design and LLM-driven architectures. By focusing on inference-first design, it’s possible to achieve significant gains in performance-per-watt, cost-per-query, time-to-first-token, output-token-per-second, and overall scalability, especially for edge and real-time applications where responsiveness is critical.
This is where the next wave of innovation lies—not in scaling training further, but in making inference practical, sustainable, and ubiquitous.
The inference trinity
AI inference hinges on three critical pillars: low latency, high throughput and constrained power consumption, each essential for scalable, real-world deployment.
First, low latency is paramount. Unlike training, where latency is relatively inconsequential—a job taking an extra day or costing an additional million dollars is still acceptable as long as the model is successfully trained—inference operates under entirely different constraints.
Inference must happen in real time or near real time, with extremely low latency per query. Whether it’s powering a voice assistant, an autonomous vehicle or a recommendation engine, the user experience and system effectiveness hinge on sub-millisecond response times. The lower the latency, the more responsive and viable the application.
Second, high throughput at low cost is essential. AI workloads involve processing massive volumes of data, often in parallel. To support real-world usage—especially for generative AI and LLMs—AI accelerators must deliver high throughput per query while maintaining cost-efficiency.
Vendor-specified throughput often falls short of peak targets in AI workload processing due to low-efficiency architectures like GPUs. Especially, when the economics of inference are under intense scrutiny. These are high-stakes battles, where cost per query is not just a technical metric—it’s a competitive differentiator.
Third, power efficiency shapes everything. Inference performance cannot come at the expense of runaway power consumption. This is not only a sustainability concern but also a fundamental limitation in data center design. Lower-power devices reduce the energy required for compute, and they ease the burden on the supporting infrastructure—particularly cooling, which is a major operational cost.
The trade-off can be viewed from the following two perspectives:
- A new inference device that delivers the same performance at half the energy consumption can dramatically reduce a data center’s total power draw.
- Alternatively, maintaining the same power envelope while doubling compute efficiency effectively doubles the data center’s performance capacity.
Bringing inference to where users are
A defining trend in AI deployment today is the shift toward moving inference closer to the user. Unlike training, inference is inherently latency-sensitive and often needs to occur in real time. This makes routing inference workloads through distant cloud data centers increasingly impractical—from both a technical and economic perspective.
To address this, organizations are prioritizing edge-based inference processing data locally or near the point of generation. Shortening the network path between the user and the inference engine significantly improves responsiveness, reduces bandwidth costs, enhances data privacy, and ensures greater reliability, particularly in environments with limited or unstable connectivity.
This decentralized model is gaining traction across industry. Even AI giants are embracing the edge, as seen in their development of high-performance AI workstations and compact data center solutions. These innovations reflect a clear strategic shift: enabling real-time AI capabilities at the edge without compromising on compute power.
Inference acceleration from the ground up
One high-tech company, for example, is setting the engineering pace with a novel architecture designed specifically to meet the stringent demands of AI inference in data centers and at the edge. The architecture breaks away from legacy designs optimized for training workloads with near-theoretical performance in latency, throughput, and energy efficiency. More entrants are certain to follow.
Below are some of the highlights of this inference technology revolution in the making.
Breaking the memory wall
The “memory wall” has challenged chip designers since the late 1980s. Traditional architectures attempt to mitigate the impact on performance introduced by data movement between external memory and processing units by layering memory hierarchies, such as multi-layer caches, scratchpads and tightly coupled memory, each offering tradeoffs between speed and capacity.
In AI acceleration, this bottleneck becomes even more pronounced. Generative AI models, especially those based on incremental transformers, must constantly reprocess massive amounts of intermediate state data. Conventional architectures struggle here. Every cache miss—or any operation requiring access outside in-memory compute—can severely degrade performance.
One approach collapses the traditional memory hierarchy into a single, unified memory stage: a massive SRAM array that behaves like a flat register file. From the perspective of the processing units, any register can be accessed anywhere, at any time, within a single clock. This eliminates costly data transfers and removes the bottlenecks that hamper other designs.
Flexible computational tiles with 16 high-performance processing cores dynamically reconfigurable at run-time executes either AI operations, like multi-dimensional matrix operations (ranging from 2D to N-dimensional), or advanced digital signal processing (DSP) functions.
Precision is also adjustable on-the-fly, supporting formats from 8 bits to 32 bits in both floating point and integer. Both dense and sparse computation modes are supported, and sparsity can be applied on the fly to either weights or data—offering fine-grained control for optimizing inference workloads.
Each core features 16-million registers. While a vast register file presents challenges for traditional compilers, two key innovations come to rescue:
- Native tensor processing, which handles vectors, tensors, and matrices directly in hardware, eliminates the need to reduce them to scalar operations and manually implements nested loops—as required in GPU environments like CUDA.
- With high-level abstraction, developers can interact with the system at a high level—PyTorch and ONNX for AI and Matlab-like functions for DSP—without the need to write low-level code or manage registers manually. This simplifies development and significantly boosts productivity and hardware utilization.
Chiplet-based scalability
A physical implementation leverages a chiplet architecture, with each chiplet comprising two computational cores. By combining chiplets with high-bandwidth memory (HBM) chiplet stacks, the architecture enables highly efficient scaling for both cloud and edge inference scenarios.
- Data center-grade inference for efficient tailoring of compute and memory resources suits edge constraints. The configuration pairs eight VSORA chiplets with eight HBM3e chiplets, delivering 3,200 TFLOPS of compute performance in FP8 dense mode and optimized for large-scale inference workloads in data centers.
- Edge AI configurations allow efficient tailoring of compute resources and lower memory requirements to suit edge constraints. Here, two chiplets + one HBM chiplet = 800 TFLOPS and four chiplets + one HBM chiplet = 1,600 TFLOPS.
Power efficiency as a side effect
The performance gains are clear as is power efficiency. The architecture delivers twice the performance-per-watt of comparable solutions. In practical terms, the chip draw stops at just 500 watts, compared to over one kilowatt for many competitors.
When combined, these innovations provide multiple times the actual performance at less than half the power—offering an overall advantage of 8 to 10 times compared to conventional implementations.
CUDA-free compilation
One often-overlooked advantage of the architecture lies in its streamlined and flexible software stack. From a compilation perspective, the flow is simplified compared to traditional GPU environments like CUDA.
The process begins with a minimal configuration file—just a few lines—that defines the target hardware environment. This file enables the same codebase to execute across a wide range of hardware configurations, whether that means distributing workloads across multiple cores, chiplets, full chips, boards, or even across nodes in a local or remote cloud. The only variable is execution speed; the functional behavior remains unchanged. This makes on-premises and localized cloud deployments seamless and scalable.
A familiar flow without complexity
Unlike CUDA-based compilation processes, the flow appears basic without layers of manual tuning and complexity through a more automated and hardware-agnostic compilation approach.
The flow begins by ingesting standard AI inputs, such as models defined in PyTorch. These are processed by a proprietary graph compiler that automatically performs essential transformations such as layer reordering or slicing for optimal execution. It extracts weights and model structure and then outputs an intermediate C++ representation.
This C++ code is then fed into an LLVM-based backend, which identifies the compute-intensive portions of the code and maps them to the architecture. At this stage, the system becomes hardware-aware, assigning compute operations to the appropriate configuration—whether it’s a single A tile, an edge device, a full data center accelerator, a server, a rack or even multiple racks in different locations.
Invisible acceleration for developers
From a developer’s point of view, the accelerator is invisible. Code is written as if it targets the main processor. During compilation, the compilation flow identifies the code segments best suited for acceleration and transparently handles the transformation and mapping to hardware, lowering the barrier for adoption and requiring no low-level register manipulation or specialized programming knowledge.
The instruction set is high-level and intuitive, carrying over capabilities from its origins in digital signal processing. The architecture supports AI-specific formats such as FP8 and FP16, as well as traditional DSP operations like FP16/ arithmetic, all handled automatically on a per-layer basis. Switching between modes is instantaneous and requires no manual intervention.
Pipeline-independent execution and intelligent data retention
A key architectural advantage is pipeline independence—the ability to dynamically insert or remove pipeline stages based on workload needs. This gives the system a unique capacity to “look ahead and behind” within a data stream, identifying which information must be retained for reuse. As a result, data traffic is minimized, and memory access patterns are optimized for maximum performance and efficiency, reaching levels unachievable in conventional AI or DSP systems.
Built-in functional safety
To support mission-critical applications such as autonomous driving, functional safety features are integrated at the architectural level. Cores can be configured to operate in lockstep mode or in redundant configurations, enabling compliance with strict safety and reliability requirements.
In the final analysis, a memory architecture that eliminates traditional bottlenecks, compute units tailored for tensor operations, and unmatched power efficiency sets a new standard for AI inference.
Lauro Rizzatti is a business advisor to VSORA, an innovative startup offering silicon IP solutions and silicon chips, and a noted verification consultant and industry expert on hardware emulation.
Related Content
- AI at the edge: It’s just getting started
- Custom AI Inference Has Platform Vendor Living on the Edge
- Partitioning to optimize AI inference for multi-core platforms
- Revolutionizing AI Inference: Unveiling the Future of Neural Processing
The post The next AI frontier: AI inference for less than $0.002 per query appeared first on EDN.
Bosch Propels Advanced ADAS Forward With Pair of Radar SoCs
Beijing IP Court denies Innoscience’s appeal against EPC’s compensated-gate patent
Who needs DC-DC converters anyway.
![]() | submitted by /u/No_Pilot_1974 [link] [comments] |
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
The post Why modulate a power amplifier?—and how to do it appeared first on EDN.
Wolfspeed appoints Bret Zahn as general manager of Automotive business
5N Plus scales up and expands critical materials supply agreement with First Solar
Дистанційне керування будівельною технікою із Yachiyo Engineering Co., Ltd
🇺🇦🇯🇵 КПІ ім. Ігоря Сікорського співпрацюватиме з японськими компаніями та організаціями щодо дистанційного керування будівельною технікою.
Alcoa exploring feasibility of gallium production in Western Australia by 2026
Kyma and Novel Crystal Technology collaborate on gallium oxide epiwafers
Pages
