Microchannel plate photodetectors, capable of picosecond time resolution and sub-mm spatial resolution, are a perfect candidate for the next generation of photodetectors for precision timing measurements. Argonne National Laboratory is producing low-cost, all-glass body, planar photodetectors with an indium seal. The design and fabrication of 6-cm square photodetectors has been well demonstrated in an ultra-high vacuum system. Recently, a new design was developed to optimize the photodetector bias voltage. This design offers an improved configuration and allows external control of the bias voltage for each internal detector component. Design and measurements of the new independently biased devices are described in this paper. We performed a systematic study on the bias voltage and achieved a gain on the order of $10^{{\mathbf {7}}}$ , a time resolution better than 35 ps, and a spatial resolution better than 1 mm.