Printed Circuit Boards
Written by a world-renowned electronics expert, this reader-friendly guide helps engineers and technicians solve issues in PCB layout, fabrication, assembly, and testing.
TABLE OF CONTENTS Printed Circuit Boards
Chapter 4: Design Considerations for Special Circuits
4.1 Design Rules for Analog Circuits
In today's world, people can easily assume that they live in an all-digital world, yet analog signals are still found within more than 60 per cent of present-day electronic designs. The three important considerations which form the basis for design rules for analog circuit PCBs are:
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Component placement;
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Signal conductors; and
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Supply and ground line conductors.
4.1.1 Component Placement
Component placement plays a crucial role, especially in analog circuits PCB design. The important guidelines to be followed in this regard are:
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Components which need to be accessed from the front panel must be placed exactly according to the requirements of the equipment designer.
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Components for internal adjustments such as potentiometers, trimmers, switches, etc. should be arranged near the board edge and placed in the proper direction for easy operation.
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Components with metal cases should not be placed very near to potentiometers, trimmers and switches etc. otherwise while adjusting, the screwdriver may cause a short-circuit between the component and the equipment chassis.
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The placing of heat-producing and heat-sensitive components must be carefully planned. Heat-producing components should be placed away from the heat-sensitive components.
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Heat-producing components should be uniformly distributed over the entire board area as far as possible. This will avoid local over-heating of the board.
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Components likely to get heated must be separated from the board surface by suitable spacers. Provision for space for these spacers should be made on the board.
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Where mounting screws need to be provided, the requisite space for nut...
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