All the pressure transducers I used (Lucas NovaSensor), requires from 1
to 2mA (constant current) for bridge excitation, and it has an impedance
around 3500 Ohms, so it will generate from 3.5 to 7 Volts across the
bridge.  The bridge output sits in the middle of that voltage, with a
full scale around 100mV, 200mV or other.  If using 5Vdc to generate the
constant current, any instrumentation amplifier (+5Vdc and Ground) will
be able to deal with the common voltages.

But for some arrange like that I would *not* use a step up power supply
based on a single transistor and a coil, instead I would go to a
Maxim641 and a coil.  But why the old 641?  Because it is one of the few
that has an internal FET *and catch diode*, and an output to drive large
FET switchers, without much fuzz.  It also regulate the output voltage
to a fixed value, without any further regulation.

I use also the Max857 with no complain at all, it has the internal FET
switcher, requires the external Schokkty catcher diode and it can not
drive an external N channel FET switcher. If you are interested to see
this one drawing, click here: http://www.ustr.net/offers/board1diags.htm
and click over the second drawing.

Wagner.