HARDWARE DESIGN TECHNIQUES

In recent years there has been much pressure placed on system designers to verify their designs with computer simulations before committing to actual printed circuit board layouts and hardware. Simulating complex digital designs is extremely beneficial, and very often, the prototype phase can be eliminated entirely. However, bypassing the prototype phase in high-speed/high-performance analog or mixed-signal circuit designs can be risky for a number of reasons. For the purposes of this discussion, an analog circuit is any circuit which uses ICs such as op amps, instrumentation amps, programmable gain amps (PGAs), voltage controlled amps (VCAs), log amps, mixers, analog multipliers, voltage references, etc. A mixed-signal circuit is an A/D converter (ADC), D/A converter (DAC), or combinations of these in conjunction with some amount of digital signal processing which may or may not be on the same IC as the converters. Switching regulators must be classified as high-speed analog circuits because of the frequencies generated by the internal or external switching action. Consider a typical IC operational amplifier. It may contain some 20-40 transistors