Ten Essential Skills for Electrical Engineers

3

HOW TO ANALYZE A CIRCUIT

Most of the analog circuits that you will encounter in the workplace and in job interviews will be fairly simple. The circuitry on most circuit boards consists of integrated components connected together by small “clumps” of interface circuitry that provide functionality such as level shifting, filtering, or signal conditioning. Frequently this circuitry is not documented, and, if you inherit the design from another engineer, you will need to figure out what it does and whether it does it correctly. This chapter shows techniques for quickly and accurately analyzing these kinds of circuits.

Analyzing simple circuits is a critical skill for job interviews, but you may question the value of this chapter when an inexpensive circuit simulator could be used to plot the frequency response for most networks. In addition to showing you how to quickly determine what a circuit does, this chapter will provide you with intuition and insight required for designing analog networks. By using the techniques reviewed here, you will not only get the analysis result, but add the circuit to your experience base and be able to modify and use it in the future. Good circuit designers always keep an arsenal of clever and useful circuits at their disposal.

Our approach to circuit analysis is as follows:

1. Simplify the circuit using techniques such as superposition and Thevenin’s theorem.

2. Write equations that describe the system.

3. Check the equations at DC and infinite ...