A circuit includes: a first swing reduction circuit coupled between an input/output pad and a buffer circuit, and a second swing reduction circuit coupled between the input/output pad and the buffer circuit. The first swing reduction circuit comprises a first transistor gated by a first bias voltage and comprises a second transistor drained by the first bias voltage. The first swing reduction circuit is configured to increase a voltage at a first node in the buffer circuit when a voltage applied on the input/output pad is equal to a first supply voltage. The second swing reduction circuit is configured to reduce a voltage at a second node in the buffer circuit when the voltage applied on the input/output pad is equal to a second supply voltage.