Measurement of the top quark charge and branching fractions at D0

We report on a measurement of the ratio $R = B(t\rightarrow Wb)/B(t\rightarrow Wq)$. In the standard model this ratio exceeds 0.998 at the 95\% confidence level. Experimentally, we measure the ratio based on the fraction of candidate events with 0, 1, or 2 b-tagged jets. We also report on a measurement of the charge of the top quark by resolving the kinematic ambiguity between the standard model scenario of a charge 2/3 quark decaying to $W^+b$ and an exotic scenario of a charge $-4/3$ quark decaying to $W^-b$.