Analog Electronics: a Structured Design Approach
Analog electronics and signal processing
Analog Electronics can be characterized as an implementation technique for information processing systems. Below, we will present a design approach for analog systems and circuits, which is based on the use of a limited number of basic analog signal processing and reference functions, the perception of information processing errors and the application of a limited number of error-reduction techniques.
Analog signal processing
Although signal processing is more and more digitally implemented, analog electronics is still indispensable for the realization of almost all electronic equipment. Important reasons are:
- With high-speed digital signal processing, the analog nature of the digital signals cannot be ignored.
For this reason, expertise of signal integrity has become very important for designers of electronics.
- When speed and power limitations of the technology become the limiting factors for the amount of information that can be processed by a digital system, analog information processing is still an interesting alternative.
For this reason, every cellular telephone is still equipped with an analog RF receiver.
The design of electronic circuits for analog signal processing, is known to be complex. Many educational programs for design engineers deal with this complexity by presenting numerous knows solutions and many tips and tricks.
Rather then focussing on known solutions (most professionals already know them) one could think of an approach that clearly separates desired functionality from its technological implementation. The concepts, the fundamental limitations to signal processing, and the design methods, are technology-independent. The final circuits and the manifestation of the information processing errors due to these fundamental limitations, differ for each technology.
Basic functions, fundamental limitations and error-reduction techniques
The design of analog information processing systems can be structured such as to facilitate system and circuit design. This design approach explicitly takes information processing as starting point for the design. It emphasizes the function of an electronic circuit rather than its appearance (circuit topology). This is the basis for a technology-independent design approach, capable of generating technology-dependent circuit solutions.
The following list briefly outlines the design approach:
- Electronic information processing systems can be built from a limited number of basic functions; the following list is believed to be complete:
Basic Function Implementation or Object Combination / distribution Combiner / distributer Amplification Amplifier Time-domain selection Switch Frequency-domain selection Filter Voltage / current domain selection Comparator/limiter Generation of voltage and current references DC reference Generation of time-domain references Timer Generation of frequency domain references Oscillator Memorization Memory Nonlinear operation Multiplier
- The amount of information that can be processed by a physical system is fundamentally limited due to:
- The addition of noise: noise limitation
- The limitation of the rate of change of a signal: speed limitation
- The limited power availability: power limitation.
- The imperfect way in which the desired function is obtained with a physical mechanism of operating principle: technological limitation.
- These fundamental physical and technological limitations cause information processing errors.
- The manifestation of processing errors depends on:
- The technology that is used for implementation of the function
- The way the information is embedded in the signal
- The observer's perception of errors
- The manifestations of errors can be reduced through application of so-called error-reduction techniques.
There are two classes of error-reduction techniques:
- Techniques that reduce the influence of component imperfections or interference sources: isolation, compensation, error-feedforward, negative feedback. These techniques do not affect the way in which the information is embedded in the signal.
- Techniques that change the way in which the information is embedded in the signal, such that the system becomes less susceptible to component imperfections or known interference sources: modulation, sampling, quantization, digitization (a combination of sampling and quantization) and coding.
