  In this work, we report the use of commercial Gallium Nitride (GaN) power
electronics to precisely switch complex distributed loads, such as electron
lenses and deflectors, without impedance matching. Depending on the chosen GaN
field effect transistor (GaNFET) and driver, these GaN pulsers are capable of
generating pulses ranging from 100 - 650 V and 5 - 60 A in 0.25 - 8 ns using
simple designs with easy control, few-nanosecond propagation delays, and MHz
repetition rates. We experimentally demonstrate a simple 250 ps, 100 V pulser
measured by a directly coupled 2 GHz oscilloscope. By introducing resistive
dampening, we can eliminate ringing to allow for precise 100 V transitions that
complete a -10 V to -90 V transition in 1.5 ns, limited primarily by the
inductance of the oscilloscope measurement path. The performance of the pulser
attached to various load structures is simulated, demonstrating the possibility
of even faster switching of internal fields in these loads. These circuits also
have 0.25 cm$\mathrm{^2}$ active regions and <1 W power dissipation, enabling
their integration into a wide variety of environments and apparatus. The
proximity of the GaNFETs to the load due to this integration minimizes
parasitic quantities that slow switching as well as remove the need to match
from 50 ${\Omega}$ lines by allowing for a lumped element approximation small
loads. We expect these GaN pulsers to have broad application in fields such as
optics, nuclear sciences, charged particle optics, and atomic physics that
require nanosecond, high-voltage transitions.
