  Tendency to bifurcate can often be utilized to improve performance
characteristics of amplifiers or even to build detectors. Bloch oscillating
transistor is such a device. Here we show that bistable behaviour can be
approached by tuning the base current and that the critical value depends on
the Josephson coupling energy $E_J$ of the device. We demonstrate record-large
current gains for device operation near the bifurcation point at small $E_J$.
From our results for the current gains at various $E_J$, we determine the
bifurcation threshold on the $E_J$ - base current plane. The bifurcation
threshold curve can be understood using the interplay of inter- and intra-band
tunneling events.
