Two recent Circuit-related articles:

Spintronics achived in plastic-GaAs hybrid circuit

Ohio State University researchers have combined traditional inorganic semiconductors with organic spintronics, in a device claimed to be the first of its kind, writes Steve Bush.

For the demonstration, the researchers used the organic magnet made from vanadium tetracyanoethylene, a polymer under development by Professor Arthur Epstein at the University, who last year demonstrated data storage and retrieval from a plastic spintronic device.

Now Dr Ezekiel Johnston-Halperin and his team at Ohio State have incorporated the plastic device into a GaAs circuit.

"In order to build a practical spintronic device, you need a material that is both semiconducting and magnetic at room temperature. To my knowledge, Art's organic materials are the only ones that do that," said Johnston-Halperin.

Spin-polarised current from a circuit in the plastic material was transmitted through the GaAs and into a LED as proof that the organic and inorganic parts were working together.

"The light was indeed polarised, indicating polarisation of the incoming electrons," said the University. "The fact that they were able to measure the electrons' polarisation with the LED also suggests that other researchers can use this same technique to test spin in other organic systems."

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System-level design explored - Embedded World

Guest columnist Mike Woodward, communications industry marketing manager at The MathWorks, describes how digital and analogue circuit simulation techniques can be combined at the system level.

Design tools are often targeted at a single design domain, for example analogue design, and don’t work well with tools for other design domains. This makes interaction between engineering teams more difficult than it needs to be.

This type of ‘silo development’ also introduces verification inefficiencies. It pushes integration testing toward the end of the design process, when bugs are more expensive to fix.

Adding to this is the tendency of engineering teams to write test harnesses from scratch, instead of using trusted models created earlier in the design process.

To link different design disciplines, we need to design and simulate different design domains in the same model. This requires a platform that can simulate different types of systems at the same time.

Multi-domain system-level design platforms do exist, combining different simulation types and tools, allowing the user to build one system model combining the behaviours of all subsystems.

Multidomain simulation can rule out unworkable designs at the start of the project. Effectively this can bring verification to project inception.

To re-use the “golden reference” system model for verification, it is necessary for the system-level design platform to have run-time co-simulation links to implementation tools that enable us to examine the dynamic behaviour of systems.

The tools, from different vendors, can exchange data at each simulation time step, enabling simulation of the dynamic behaviour of the analogue-digital system. Similar co-simulation links are also available for other popular analogue and circuit-level simulation environments.

This co-simulation offers three benefits. First, it re-uses the system-level model as a test bench during the implementation phase of the project.

Second, the system model acts as a common simulation platform between different disciplines, enabling collaboration via a common model all can understand and use.

Third, we can benefit from a more integrated development approach while still using existing tools, reducing adoption risk. This early verification has yielded large savings in several real projects.

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