We explore the chiral transmission of electrons across graphene heterojunctions for electronic switching using gate geometry alone. A sequence of gates is used to collimate and orthogonalize the chiral transmission lobes across multiple junctions, resulting in negligible overall current. The resistance of the device is enhanced by several orders of magnitude by biasing the gates into the bipolar npn doping regime, even as the ON state in the homogeneous nnn regime remains highly conductive. The mobility is preserved because the switching involves the suppression of transmission over a range of energy (transmission gap) instead of a structural band gap that would reduce the number of available channels of conduction. Under a different biasing scheme (npn to npp), this transmission gap can be made highly gate tunable, allowing a subthermal turn-on that beats the Landauer bound on switching energy, limiting present-day digital electronics.