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Two Critical Circuit Debugging Techniques

Key Takeaways

  • The act of analyzing a circuit and detecting and correcting any errors is called circuit debugging.

  • The two most common circuit debugging techniques are the functional area approach and the split-half method. 

  • Circuit debugging techniques are backed by test equipment such as analog or digital voltmeters, multimeters, function generators, oscilloscopes, transistor testers, and regulated DC power supplies.

Using circuit debugging techniques

During college, I participated in a circuit debugging competition. I remember being surprised at how challenging it was; in the end, I could not debug the circuit. I walked away from the debugging competition with a new respect for the craft—the act of circuit debugging is an art by itself. Luckily, in the later years of my career, I learned that there are circuit debugging techniques that make the troubleshooting process much easier. A good strategic approach to circuit debugging prevents avoidable mistakes. 

What Is Circuit Debugging?

It is common for hardware engineers to experience non-functional circuits when a complex design is rigged up for the first time. The non-functioning of the circuit can be due to faulty components, errors in the wiring, shorts, improper connections, circuit breaks, incorrect equipment settings, etc. The act of analyzing a circuit and detecting and correcting any errors is called circuit debugging. Circuit debugging helps get rid of problems associated with the circuit. By circuit debugging, any circuit malfunction is corrected and the circuit can give the desired performance. 

As the complexity of the circuit increases, circuit debugging faces significant challenges. The type and count of bugs in the circuit make circuit debugging a time-consuming process. 

Types of Circuit Bugs

The bugs in a circuit can be classified into:

  1. Constructional errors or bugs: When a design is not matching with the constructed circuit, constructional errors can form. The most common causes of constructional errors are short circuits, open circuits, fabrication defects, improper connections, and faulty components. 
  2. Conceptual errors or bugs: Whenever there is a mismatch between the specification and the design, it can lead to conceptual errors. Operating the circuit components above their ratings and connecting the components incorrectly are two examples of conceptual errors in circuits. 
  3. Intermittent errors or bugs: Intermittent errors are circuit errors caused by external interferences in a correct circuit. External interferences can be electrical noise signals, thermal noises, or shocks.  

Circuit Debugging Techniques

Circuit debugging requires a clear understanding of the circuit diagram and how it works. Knowing the design and the circuit operation are important assets while performing circuit debugging. The designer of the circuit that needs debugging is therefore in the best position to successfully debug the circuit.

Apart from a familiarity with the design, years of experience working on hardware circuits also provide insights that could be advantageous in solving complex circuit issues. An experienced engineer can follow a systematic approach to circuit debugging and rely on proven debugging hacks or techniques for quick troubleshooting of circuits.

The Debugging Process

The circuit debugging process starts with the establishment of the fault or bug in the circuit. Once the fault establishment is confirmed, the fault area or component is located. The fault in the circuit is corrected and the debugged circuit is tested to ensure its expected functionality. The circuit debugging technique that is used depends on the circuit type. The two most common  circuit debugging techniques are:

  1. Functional area or block diagram approach - A circuit can be divided into different sections or functional areas such as power supply, oscillator, amplifier, rectifier, etc. In the functional area approach, the functional areas that are working properly are removed from the list and the ones with faults are isolated. The faulty functional areas are analyzed and the faulty component(s) are identified. The faulty area or component is replaced to make the circuit operational. 

  2. Split-half method - In the split-half method, the circuit is bifurcated and the outputs at the halfway point and output terminals are checked. This approach helps to identify the location of the fault–either in the first half or second half. The faulty section is again split into two halves and the same procedure of circuit debugging is carried out. The splitting process continues until the faulty functional area or component is isolated. The split-half circuit debugging plan of action changes with the presence of convergent, divergent, and feedback paths in the circuit. 

Circuit debugging techniques are backed by test equipment such as analog or digital voltmeters, multimeters, function generators, oscilloscopes, transistor testers, regulated DC power supplies, etc. The pre-layout and post-layout tools from Cadence’s suite of PCB design and analysis tools can be used for printed circuit board debugging.

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