Intrinsic evolution of digital-to-analog converters using a CMOS FPTA chip

  • Langeheine J
  • Meier K
  • Schemmel J
 et al. 
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The work presented here tackles the problem of design-
ing a unipolar 6-bit digital-to-analog converter (DAC) with
a voltage mode output by hardware evolution. Thereby a
Field Programmable Transistor Array (FPTA) is used as the
analog substrate for testing the candidate solutions. The
FPTA features 256 programmable transistors, whose chan-
nel geometry and routing can be configured to form a large
variety of transistor level analog circuits. A series of experi-
ments reveals that variations of the output voltage range in-
fluence evolution’s success more severely than varying the
amount of available electronic resources or the geometri-
cal setup. Although a considerable number of runs yield
converters with a nonlinearity of less than 1 bit, no DAC is
found to maintain a nonlinearity of less than 0.5 bits under
worst case conditions, as required for a true 6-bit resolu-
tion. While the evolved circuits work comparably well at
different time scales as well as on different dice, they lack
the ability to abstract from the analog voltage levels of the
digital input signals. It is experimentally verified that this
can be remedied by inserting digital buffers at the circuits’

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  • Jörg Langeheine

  • Karlheinz Meier

  • Johannes Schemmel

  • Martin Trefzer

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