In the BTL configuration, two amplifiers are connected together in a bridge configuration. In this configuration, the output signal of one amplifier is switched inverted to the input of the second amplifier. While the first amplifier operates as a voltage amplifier, the second amplifier, which receives the signal in phase opposition, operates as a current amplifier. Since both the signal voltage and the signal current are amplified, this results in a disproportionately high power amplification. If both amplifiers each double the audio signal, this results in four times the output power.