Bridge-Tied Load

Definition

Used in audio applications, the load (a speaker in this case) is connected between two audio amplifier outputs (it "bridges" the two output terminals).

This can double the voltage swing at the speaker, compared to a speaker that is connected to ground. The ground-tied speaker can have a swing from zero to the amplifier's supply voltage. A BTL-driven speaker can see twice this swing because the amplifier can drive either the + terminal of the speaker or the — terminal, effectively doubling the voltage swing.

Since twice the voltage means four times the power, this is a major improvement, especially in applications where battery size dictates a lower supply voltage — e.g. automotive or handheld applications.

Synonyms