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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?

 

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  • 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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  • 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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