19 Replies Latest reply on Mar 5, 2020 4:46 AM by saicheong

    Why Is Analog Design Harder Than Digital Design?

    rscasny

      Are you an analog design engineer or digital? By most standards, the marketplace is producing more digital design engineers than analog. Ask most engineers and they would tell you why: analog design is harder than digital, and requires more knowledge and more factors to consider such as a deep understanding of efficient power, precision measurement, wireless connectivity, and reliable circuit protection. What  do you think?

       

      Let's talk about that a bit more. Is analog design just a matter of knowledge, or is there something more involved? It likely boils down to that fact that analog design involves more than just analog. It's influenced by circuit theory, signal processing, control systems, and device physics, and more. When you consider that circuits and components are more integrated and operated at ultra low power, one needs to consider both pow power, low noise, and stability over the required temperature range.

       

      What's analog design require? Efficient power ICs to extend the lifetime and reduce heat dissipation for your design. Precision measurement ICs to feature high accuracy and high performance for across-the-board precision analog applications. Rugged connectivity to offer the industry’s highest level of protection for connectivity in hazardous environments. Reliable protection ICs to protect systems from faults by maintaining and monitoring proper voltage, current, and temperature levels.

       

      For sure, analog design has always been more complicated than digital design. While both require the engineer to make design compromises, analog beats digital design in the arena of complexity. All the variables involved just make it nothing but hard.

       

      I've told you what I think. How about you?

       

      Why do you think analog design is more difficult than digital design? If you have an example, share it with the element14 community?

       

        • Re: Why Is Analog Design Harder Than Digital Design?
          genebren

          Digital is On or Off, where Analog is continuous.  Because of this difference, designing Analog circuits becomes much more difficult, as there are so many considerations that need to taken into account.  Temperature, noise, power signals can all effect an analog circuit.  In an Analog circuit, all of these forces need to be understood and compensations need to be designed in to the circuit to prevent them from influencing the intended functionality.  A simple opAmp circuit is relatively easy to understand, but how to prevent outside forces from effecting this circuit is much more complex.  I remember a simple saying, "amplifiers oscillate, oscillators don't"  that hints at how difficult it can be to achieve the functionality you want to occur, without having unintended results. 

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          • Re: Why Is Analog Design Harder Than Digital Design?
            neuromodulator

            I think digital is more of an illusion as signals are analog, and that fact will at some point have practical implications even if one tries to ignore that. I also think not that many are into analog because it requires a lot of math and physics, which is something I don't think many enjoy, specially when you get into differential equations, modelling and statistics.


            This post reminded me of Bob Widlar, one of the pioneers of analog ICs who had had some pretty strong (and offensive), but kinda funny opinions on digital design:








            • Re: Why Is Analog Design Harder Than Digital Design?
              colporteur

              I would challenge the statement "Analog Design Harder Than Digital Design". Define harder for me?

               

              Either discipline taken into the real word (i.e practical application) is hard. What cushions the application of the discipline is experience. You could argue knowledge is also a cushion but I have found it only works well after the fact

               

              I tell the story of an RF engineer designing a radio transmission/receiver system. The individual was an iron ring engineer and I was a technologist. The site we were working on, had reception issues. The replacement design was suppose to resolve the issue. The engineer design used the latest technology. He used the engineer specifications of the replacement equipment to maximize the RF energy available.

               

              After reviewing his design I asked him some questions regarding theory applied. I agreed the specification indicates the RF connections has .5dB  loss. If that connection was made by an installer in -35 Celsius temperature and the cable was rolled out in a snow storm would he still feel confident in his design. My comments were to help him understand what happens in the real world.

               

              I continue to discover, even after retirements, what works in the my lab doesn't work the way I think it should when it meets the real world. I thought this pic was a great visual of applied theory.

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              • Re: Why Is Analog Design Harder Than Digital Design?
                dubbie

                I am of an age when studying a BSc Electrical & Electronic Engineering was still mostly analogue (one of my first year courses was on designing with valves - the vacuum type). Then I had a course on digital circuits. Wow! Amazing! It was just so easy and it worked (virtually) every time. It was several years later that I actually really understood that even digital circuits were really analogue circuits. Still, by then microprocessors were abounding and I could even stop worrying about digital stuff. I still also remember a lecture or course I did on communication theory (possibly when I was trying to understand one of Alan Turing's paper on computing) when I realised that digital values mean whatever I want them to mean and were not absolute values. Good days.

                 

                Dubbie

                • Re: Why Is Analog Design Harder Than Digital Design?
                  lui_gough

                  I find analog design harder than digital design because of a number of hurdles:

                  • The maths - analog design is very math heavy and I found that quite challenging to get my head around.
                  • The "non-idealities" of reality - while it's easy to simplify components and think of them as "ideal" resistors/capacitors/inductors, in real life, the non-idealities can easily come to bite you in the butt - so what may work in theory doesn't work (or doesn't work well) in practice.
                  • Problems with simulation - I've had a good amount of fun with Pspice/LTspice, but it's not easy to simulate complex circuits realistically - again, shortcuts we take with the models here often yield simulation results that don't match real-life performance.
                  • Cost - unlike digital circuits which can often be easily digitally reconfigured (as software), analog circuits often result in needing specific components (which means having a good stash of them) and occasionally letting out blue magic smoke.
                  • The unforgiving nature of the signal - analog signals are exactly that. There is no "leeway" in interpretation - so whatever inadequacies are in the circuit will degrade the output (e.g. noise). The design has to be done much better and with more care than with digital signals that have a wide threshold between values and are tolerant of imperfections, especially when error-correcting codes are involved.
                  • The "dark arts" - some specific analog fields, such as RF, are still often referred to as dark arts as they can be difficult to prototype without getting stray inductances/capacitances dominating. To troubleshoot these designs takes a lot of knowing-rules-of-thumb and luck.
                  • More difficult debugging - a demanding analog design is not particularly easy to debug as the probes will often change the value of the signal due to loading or not read the expected signal/introduce corruption into the signal.

                   

                  As a result, I tend to like digital - it's simpler even though technically everything is "analog" to begin with, digital methods merely interpret the analog as one of several states, making it more tolerant and allowing us (most of the time) to abstract the analog complexity away to just the first few blocks of a circuit that deal with input and output. I suppose a good illustration of this is the explosion of Software Defined Radio (SDR) in even consumer-grade products.

                   

                  - Gough

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                  • Re: Why Is Analog Design Harder Than Digital Design?
                    dougw

                    Until digital becomes analog (high frequency) it is a bit like a cookbook - just follow the datasheet.

                    With analog, the datasheet is just the start of an adventure.

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                    • Re: Why Is Analog Design Harder Than Digital Design?
                      DAB

                      Digital is a subset of Analog.

                       

                      The boundaries of digital design are fairly easy to establish.

                      In Analog, you have a more open set of criteria that make a good circuit more challenging.

                       

                      DAB

                        • Re: Why Is Analog Design Harder Than Digital Design?
                          dougw

                          Interesting perspective. I used to work with a bunch of physicists who bragged that chemistry was a subset of physics, but that didn't mean they were knowledgeable about chemistry.

                            • Re: Why Is Analog Design Harder Than Digital Design?
                              DAB

                              If you are a physicist, then you need a working knowledge of Chemistry if you are involved with elements.

                              If you are a chemist, you need a working knowledge of physics, depending upon what depth of elements and compounds you need to work with.

                               

                              Digital engineers study circuits that have timing and decision making involved.

                              Analog engineers study circuits in which a much wider range of possible events within its solution.

                               

                              I agree that as digital has gotten much higher speeds, the analog effects are introducing a wider range of issues than they did back in the early days of digital IC circuits.

                              Analog however still remains a wide open domain requiring a very specific set of skills, usually much deeper than those needed to do basic digital circuits.

                               

                              I would never ask a digital engineer to do an analog circuit and vice versa.

                              They are two different domains requiring two different mind and skill sets.

                               

                              DAB

                                • Re: Why Is Analog Design Harder Than Digital Design?
                                  dougw

                                  True. For example if you wanted to design a multiplication circuit using gates, op-amps and transistors. It is pretty tricky whether you design a digital multiplier or an analog multiplier. I wouldn't say one is easier than the other - it just depends on your experience.

                                  • Re: Why Is Analog Design Harder Than Digital Design?
                                    genebren

                                    There are tremendous amounts of overlap of skills between analog and digital design, and a set of building blocks (laws and theorems) that are common knowledge for either disciplines.  That too is true for electronics and other science fields.  One of the best engineers that I ever had the privilege of working  with was actually a PHD physicist.  His physics background was so helpful in understanding the lower level reasons (and theoretical limits) of electronics, especially as it applied to the life sciences application we were working with (pressures, fluidics, light, etc.).

                                      • Re: Why Is Analog Design Harder Than Digital Design?
                                        DAB

                                        Hi Gene,

                                         

                                        Agreed, there are a lot of overlap, but there are also very keen differences.

                                        It all depends upon what type of analog circuit you are dealing with and what parameters are involved.

                                         

                                        In my experience with advanced aerospace projects, you need very good specialist in both areas to make the project work.

                                         

                                        DAB

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                                    • Re: Why Is Analog Design Harder Than Digital Design?
                                      dubbie

                                      Douglas,

                                       

                                      I thought Chemistry was a sub-set of physics!

                                       

                                      Dubbie

                                  • Re: Why Is Analog Design Harder Than Digital Design?
                                    dougw

                                    I don't think I answered the question earlier.

                                    I don't think of digital as easier or harder than analog. I started out very keen on digital but ended up spending just as much time on analog and I now like both.

                                    I apply the same level of rigor to both digital and analog when designing circuitry, so for me they are about the same hard.

                                    • Re: Why Is Analog Design Harder Than Digital Design?
                                      michaelkellett

                                      I voted

                                      I am primarily an analog design engineer.

                                      and then realised that I was the first out of 26 to do so !

                                      Actually I'm primarily an analogue design engineer but there wasn't an option for that

                                       

                                      I do spend a lot of time doing digital stuff, mainly micros and FPGA but very often the heart of a design will be analogue.

                                      Often the software side will take longer but the real enabler is analogue - for example in a weighing system I worked on recently most of the design time went into the micro and the Bluetooth interface but the harder part was getting the load cell interface, ADC and power supply (complete with battery management), right, and testing it to prove it's right.

                                       

                                      But like many others who have already commented - I wouldn't quite call out one of analogue or digital as harder - it rather depends on how ambitious you are.

                                       

                                      MK

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                                      • Re: Why Is Analog Design Harder Than Digital Design?
                                        kamtar

                                        I would say that it's simple: Digital design is more about working within artificial systems designed by other people. Analog is more about fighting with laws of physics.

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                                        • Re: Why Is Analog Design Harder Than Digital Design?
                                          saicheong

                                          Nobody will say design a CPU is an easy task or use digital sensors is already easy that use an analog sensors, or say bluetooth is easier that FM analog.

                                          It depending on what we working for.

                                           

                                          People believe digital is easier that the analog because currently the most powerful and flexible human make computer system is digital,

                                          , we package the logic in software, run in a very complex machine with more that billion components, and make those Abstraction.

                                           

                                          In current technology, most of the case we use ADC transfer analog to digital signal, process it and translate back to analog signal by DAC is easier that direct face of analog, it is because the digital signal is well define, mathematisation of data, error prove, our digital computer is powerful and flexible and cheap by mass production that analog, we use digital to hold the complex thing and make outside (analog) simpler.

                                           

                                          As Randall say that Power IC is analog design, which is the point of view for Application Engineering ( IC customers), however most Power IC use embedded digital MPU for the heart, as monitor the voltage and current by ADC, implement soft startup, and control MOSFET ON/OFF for precision outputs help to reduce the external components and complex of analog circuits.

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