Axiom

 
Achieving High Power RF in Mainstream CMOS

Axiom’s patented Distributed Active Transformer (DAT) technology is a circuit technique which works well with a conventional CMOS process technology – as  it does not require any specialist or proprietary process extensions.  Multiple differential amplifiers feed multiple primaries   In the example shown below there are 4 differential amplifiers feeding 8 primaries.  Each primary is a single slab of metal connecting the drain of one branch of the differential pair with the DC supply feed.    The secondary is a single loop.  The transformation ratio is given by the number of primaries rather than a ratio of turns as in a conventional transformer  The impedance may be tuned to exactly 50Ω by means of the capacitors connected in parallel with the differential pairs   The output is naturally differential, but it typically configured as a single ended structure by simply grounding one terminal.  Normal CMOS processes may be used as the DAT geometry alleviates typical de-Qing effects experienced in a typical spiral inductor.

DAT

Axiom’s patented Distributed Active Transformer (DAT)


The advantages of this approach are numerous:

  • Power combination and impedance transformation in one elegant structure
  • Differential to single ended conversion “for free”
  • High passive efficiency structure which is compatible with high active efficiency switching amplifiers
  • Output match is broadband, and therefore can cover multiple frequency bands
  • A high transformation ratio can be realized to allow low drain voltage CMOS operation, while still allowing a wide operating frequency range
  • 50 ohm match is on-chip so the external passive components are eliminated
  • Inexpensive packaging can be used thus eliminating the requirement for multi-chip module technology
  • Improved reliability of single-chip CMOS
  • The DAT technology provides the silicon designer with the possibility to develop extremely low cost high performance cellular power amplifiers.

    Axiom’s technology represents a technology discontinuity in power amplifier design and we believe the advantages are significant for our customers.