The design and implementation of a submicron-silicon bipolar parallel processing master-slave D-type flip-flop decision circuit, operating at data rates as high as HGbit/s is described. This is the fastest reported decision circuit for silicon bipolar technology. The ICs used in the hybrid circuit were fabricated using a 0-6/an, non-polysilicon emitter technology, and mounted in a package employing coplanar waveguides. © 1990, The Institution of Electrical Engineers. All rights reserved.