A disclosed embodiment is a switching circuit including a number of transistors fabricated in a device layer situated over a buried oxide layer and a bulk semiconductor layer. Each transistor has a source/drain junction that does not contact the buried oxide layer, thus forming a source/drain junction capacitance. The disclosed switching circuit also includes at least one trench extending through the device layer and contacting a top surface of the buried oxide layer, thus electrically isolating at least one of the transistors in the switching circuit so as to reduce voltage and current fluctuations in the device layer. The disclosed switching circuit may be coupled to a power amplifier or a low noise amplifier and an antenna in a wireless communications device, and be controlled by a switch control signal in the wireless communications device.