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Analog Angle Blog

What Makes a Great Analog IC?

We've all encountered an analog IC that simply makes you stop and say “wow.” So how does an IC reach this status level?

Certainly, there's low price — but I don't really consider that the mark of a great IC, since it is not a technical virtue. After all, a vendor can decide to low-ball the price and make very little or no margin on it, or even chose to take a loss, perhaps to buy into a market (“We lose money on every one, but we plan to make it up in volume”).

Of course, sometimes the low price is the result of a radically new internal architecture or process enhancement, or even a production test technique that allows them to charge less and still make a decent margin — but I'll leave that angle for another time.

For me, there are three technical factors for which an analog IC can be especially noteworthy:

First, having a greatly improved and superior specification. Sometimes, a vendor dramatically improves a vital parameter, or manages to make a pretty good improvement in one spec yet without incurring the usual tradeoffs that such an improvement has traditionally required (for example, speed versus power). Or the part hits a “sweet spot” with just the right combination of specifications, and which wasn't previously achievable.

Second, providing an added function or feature which makes it much easier for the circuit designer. This is more than just packing more functional blocks onto the die. It means realizing that many designers are using the part to do “x” but they often also have to add an external something. By combining that extra feature with the basic function, the designer's project would be so much easier. It may be mostly just realizing that adding even the fairly mundane function to a high-performance part yields a case where 1 + 1 > 2.

Finally, there are the real head-turners, which do something that hasn't been done before. This doesn't necessarily mean integrating a lot of stuff onto an IC — it's when the IC design team uses the singular potential of monolithic technology to implement something truly innovative.

An example of simplicity is the AD590 monolithic temperature sensor from Analog Devices, introduced decades ago and still available for new designs. It exploits the temperature sensitivity of silicon to pass a current proportional to the temperature (1 μA/°K), and does so with a relatively simple IC comprised of just a few active devices. But what users really like is this: It's easy to use, small, rugged, and does what it is supposed to do, without complications (and yes, it is low cost).

A more recent example is the AS3935 Franklin Lightning Sensor IC from AMS (formerly Austriamicrosystems). When I first saw the announcement and background press package, I thought, “Whoa, this is something really different.” This small IC tackles a problem for which the only alternative solutions have been boards and boxes which may not even work as well, unless they are fairly complex and expensive instruments.

Have there been any ICs that really impressed you? In which one (or more) of the three above ways did they do so?

11 comments on “What Makes a Great Analog IC?

  1. jkvasan
    February 23, 2013

    I fully agree with you on the AD590 device. It had made designs very simple and makes life easier with a straight forward output. I remember LM35 being another temperature sensing device for the same reasons.

    ICL8038 is another IC I would like to mention. It is a nice function generator with square, triangle and sine wave outputs with an amazing frequency range from 0.01 Hz to 300 Hz.

  2. Bill_Jaffa
    February 23, 2013

    Yes, the Intersil ICL8038 was(is) a great part–lots of hobbyists used it as the core of a low-cost, decent function generator. (BTW, I think you meant 300 kHz, not 300 Hz.)

    Interesting history note: Intersil is a relatively old semi company, founded in 1967 by Jean Hoerni, one of the famous eight who left Schockley Transistor Labs to form Fairchild Semi. There, he was instumental in development of the planar semiconductor process–a radical and truly significant advance in transistor processes. And Intersil has had a wild history–owned by GE for a while, then Harris, then spun off again as an independent company.

    I don't know to what extent, if any, he was involved in the development of the 8038–does anyone out there know or can cite and references on 8038 history?

  3. David Maciel Silva
    February 24, 2013

    Some options of the integrated circuits surprising, some temperature sensors e.g. can have the values alarm configured through command I2C.

    After a specific problem for interpretation of load cells and temperature sensors with different scales came across the need to change the gain of a circuit operating without alteration or adjustment in hardware, which would imply a technician making adjustments or changes components (resistors, trimpot's), for each type of sensor being used.

    Through research, I found the integrated circuit: MCP6S21, which is a Programmable Gain Amplifiers.

    This iten surprised me too …

  4. Brad Albing
    February 26, 2013

    Quite right – a vey nice part that I used in several great home projects. Intersil obsoleted that part some time ago. I think Exar makes a similar function generator device.

  5. Brad Albing
    February 26, 2013

    In all the bazillion designs I've done, I've never used a PGA. I should look into that sometime.

    Vaguely related design concept: An op-amp or an IA (instrumentation amp) that uses a DCP (digitally controlled pot) to set the gain. Recall that there is a topology of the IA that permits gain changing with one gain-setting resistor. Then, use a DCP that can be controlled via an I2C bus – et voila! A PGA controllable by an I2C bus.

  6. KRS03
    February 27, 2013

    Bill,

    Certainly the 8038 was designed under the direction (VP of Engineering) of Dave Fullagar.  Intersil was on the forefront of CMOS as well as Bipolar analog IC design at that time.  The first digital watch chip (for Casio I believe) was designed and produced there.  Fullagar of course designed the μA741 Op Amp while at Fairchild and went on later to become a co-founder of Maxim.

  7. Bill_Jaffa
    February 27, 2013

    And another I just remembered: the NE565 analog PLL IC from Signetics (another name lost in the ether), designed, I believe, by Dr Alan B Grebene.

  8. SunitaT
    February 28, 2013

    I remember LM35 being another temperature sensing device for the same reasons.

    @Jayaraman, yes LM35 was another great Analog IC. I have used this IC in many of my projects. Am curious to know what IC do you use to generate frequencies greater than 300Hz ? Any recommendations ?

  9. amrutah
    February 28, 2013

    Since decades having the silicon Tempco controlled to this level is a great achievement from the Fab Team…

  10. kvasan
    March 1, 2013

    Sunita,

    Have you tried XR2206, it can generate frequencies from 0.01 Hz to 1 MHz.

  11. SunitaT
    March 1, 2013

    Have you tried XR2206, it can generate frequencies from 0.01 Hz to 1 MHz.


    @kvasan, No I haven't tried that IC. Thanks for sharing the info. I have made a note of it.

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