Adaptive silicon comes to RF

The idea here is that you can modify the device's characteristics with extreme precision by adding electrons to the floating gate using impact-ionized hot electron injection (the transistor on the left), or by removing them using Fowler-Nordheim electron tunneling (the transistor on the right).

Of particular interest is the fact that hot electron injection is a relatively new phenomenon in the case of PMOS transistors (most folks do it with NMOS devices). However, it turns out that there are significant advantages to using PMOS transistors, not the least that they require only a minute amount of current -- in the order of nanoamps - for the hot electron injection to take place. By comparison, achieving hot electron injection in NMOS devices requires the use of charge pumps to supply the necessary current, which can be hundreds of micro amps or even milliamps.

In addition to offering benefits in terms of reliability, the low currents required by the PMOS devices mean that you can be injecting electrons while the circuit is in operation, which allows these devices to support active tuning as discussed below.

This really is a cool beans technology
When you create an analog circuit, it's often critical to have pairs of matched transistors operating together. Any mismatches arising from the manufacturing process can be disastrous in terms of signal quality and power consumption. This is of course why analog components are often created on exotic materials in the first place - to allow for much finer control of the transistor's characteristics. The point is that, using Impinj's pFET devices, you can modify the characteristics of the transistors after they've been manufactured, which means you can fine-tune the circuits so as to achieve optimal results.

One key point that is very important to understand that these pF ETs can be implemented using any standard (low cost) CMOS process, and are compatible with the digital CMOS technologies offered by TSMC, UMC, or Chartered. In turn, this facilitates combining the analog/RF and digital baseband functions on the same SoC.

It's also important not fall into the same trap I did. When I first saw material on Impinj's technology, I mistakenly thought that the entire analog/RF portion of the design was to be created out of pFETs. In fact this is very far from the case. For example, Impinj's first "proof-of-concept" product is a 14-bit DAC, which contains several thousand transistors, of which only 31 are pFETs.

The point is that, even using only this small quantity of pFETs, the ability to fine-tune the device post-manufacturing means that it only consumes 50 milliwatts of power while running at 300 mega-samples per second (Impinj told me that comparable devices consume 500 to 700 milliwatts). Furthermore, the Impinj device provides a SPDR (spur-free dynamic range ... what ever that is) of 80dB, which is apparently 6dB better than its closest competitor.

The really cool thing is that Impinj's technology doesn't change the core functionality of the analog/RF circuits - an amplifier is still an amplifier, a D/A converter is still a D/A converter - and so forth. What Impinj brings to the party is the ability to continuously calibrate and configure the functions forming an analog device. This provides for new ways of compensating for environmental (voltage and temperature) fluctuations, and also offers significant benefits in terns of design portability when migrating an existing design, or portion thereof, to a new technology node.

It's well worth noting that Impinj was called one of "the most original and promising companies formed in the last few years" by the MIT Technology Review in September 2001. It looks like Impinj's self-adaptive silicon could well be a "disruptive technology," which always means more fun and excitement for designers and consumers ... so I think that this has to receive an official "Cool Beans" from me. Until next time, have a good one!