  Controlling the electronic structure of two-dimensional materials using the
combination of twist angle and electrostatic doping is an effective means to
induce emergent phenomena. In bilayer graphene with an interlayer twist angle
near the magic angle, the electronic dispersion is strongly modified by a
manifold of hybridizing moir\'e Dirac cones leading to flat band segments with
strong electronic correlations. Numerous technical challenges arising from
spatial inhomogeneity of interlayer interactions, twist angle and device
functionality have so far limited momentum-resolved electronic structure
measurements of these systems to static conditions. Here, we present a detailed
characterization of the electronic structure exhibiting miniband dispersions
for twisted bilayer graphene, near the magic angle, integrated in a functional
device architecture using micro-focused angle-resolved photoemission
spectroscopy. The optimum conditions for visualizing the miniband dispersion
are determined by exploiting the spatial resolution and photon energy
tunability of the light source and applied to extract a hybridization gap size
of $(0.14 \pm 0.03)$~eV and flat band segments extending across a moir\'e mini
Brillouin zone. \textit{In situ} electrostatic gating of the sample enables
significant electron-doping, causing the conduction band states to shift below
the Fermi energy. Our work emphasizes key challenges in probing the electronic
structure of magic angle bilayer graphene devices and outlines conditions for
exploring the doping-dependent evolution of the dispersion that underpins the
ability to control many-body interactions in the material.
