Page 57 - Analog Circuit Design Art, Science, and Personalities

Reflections of a Dinosaur

vcc (+15 volts)

than the binary weighted converter (one resistor per switch) and significantly less
Figure 6-8.
Hybrid Systems’ than the current division configuration (three resistors per switch).
By combining and modifying existing circuits, new circuits can be created that
DAC 37,-8 are better suited for a particular application than the circuits from which they were
8-bit DAC.
derived.
Performance is not the only parameter that can be optimized by modifying exist-
ing circuits. Performance can sometimes be traded off for other variables such as
cost and size.
In the early 1970s Hybrid Systems (now Sipex) was looking for a technique to
build a “cheap and dirty” digital-to-analog converter that could be given away as a
promotional item. At the time, the circuit of Figure 6-6, or some slight variation,
was the configuration used by most converter manufacturers. This circuit was too
expensive to give away, so a modification was in order. We modified the circuit of
Figure 6-2 by replacing all the switching transistors with diodes (see Figure 6-7).

Figure 6-9.
lnternals of
Hybrid Systems‘s
DAC 371 -8.

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