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I've been looking over some board designs and have been trying to identify the reasons behind using resistor networks over individual resistors. Some guesses I can think of are a reduced part-count and complexity. Does it also follow that a design using a resistor network is cheaper than one that uses individual resistors? Because of this, I would think one would try to maximize use of networks, but many of the designs use several individual resistors instead and I can't figure out why.

And a separate but relevant question: are capacitor networks in the same boat?

Crunchy
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2 Answers2

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Typical advantages of using resistor networks:

  • Smaller part count, as mentioned. Therefore faster assembly.
  • Better matching of individual resistor values and drift, by being in the same package.
  • Saving board space: Not always, but when you account for the keepout area for individual parts, it's an even bet.
  • Cost of BOM: Not necessarily, but for sufficient volume, almost certainly.

Why every design does not use resistor networks:

  • Availability - Not as ubiquitous as individual resistor values
  • Coupling between resistors: Especially a risk with the smaller network packages
  • Cost: For smaller volumes, likely to be more expensive than the individual resistors
  • Layout convenience: It can sometimes get exasperating to fit traces around a 8-lane highway toll bridge of a network.
  • Flexibility: All the resistors in a network are typically the same value (R-2R networks do exist), while actual designs do not always need 4 or 8 resistors of the same value at the same location on the board.
  • As @ThePhoton mentions in his answer: Tolerances available
Anindo Ghosh
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  • I find that the layout convenience often results in a smaller overall PCB area, even once you factor in the keepout area of individual resistors. –  Jul 23 '13 at 19:14
  • @DavidKessner Agreed. Case-to-case, board-to-board, even bets either way. Also, here in India, getting local supplies of SMD resistor networks is . – Anindo Ghosh Jul 23 '13 at 19:23
  • @DavidKessner Do you mean the layout convenience from the resistor network? So the resistor networks reduce the overall PCB area more often than not? – Crunchy Jul 23 '13 at 21:48
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    @Crunchy No, the layout convenience of individual resistors. With a resistor net, all of the resistors are in the same place on the PCB. With individual resistors I can place them where it makes sense from a routing perspective. With a network, all of the resistors are in a central location and the routing has to accommodate. For many (but not all) circuits, the additional routing of a resistor network might take more space than the same circuit with individual resistors. –  Jul 24 '13 at 00:37
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Resistor networks generally take up less space than an equivalent number of discrete resistors.

And placing a resistor network involves only a single pick-and-place operation, which could reduce your assembly costs.

On the other side, networks are generally only available off-the-shelf in 5% tolerance, so if your design requires 1% or better you might prefer individual resistors.

Some reasons to prefer individual resistors:

  • You need to place the different resistors in physically separate locations (for example, to minimize track lengths)

  • You might need to change a resistor value while debugging your circuit, and you won't want to have to change several values in the same way.

The Photon
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