Bridged and paralleled amplifiers

Depending on the method of combining separate amplifiers, bridging or paralleling, different amplification goals can be served.

This approach can be beneficial for driving loads for which using a single-ended amplifier is impossible, impractical or less cost-effective.

This equation also shows that bridging quadruples the theoretical power in an amplifier, however this is true only for low enough loads.

For example, for loads where the amplifier reaches its full potential in single-ended mode, there is no gain to be made with bridging.

The load is connected between the “hot” (often red) outputs of the two amplifiers, and is subject to the potential difference between them.

[3] The provision of the anti-phase audio input signal can be provided in several ways, which require appropriate knowledge and skill.

Amplifier circuits are typically designed with the lowest-cost components needed to provide the desired performance characteristics.

The bridge mode option is often used in PA systems and especially in car audio applications to feed bass loudspeakers at high power.

These resistances are necessary because the output impedance of the two amplifiers will not, due to manufacturing variation, be perfectly identical.

Introduction of output resistors isolates this imbalance and prevents problematic interactions between the two amplifiers.

The two topologies complement each other in that the bridging allows for higher voltage output and the paralleling provides the current handling capacity needed to drive low impedances, typical in subwoofer applications.

It is more commonly used with IC power amplifiers with stereo outputs operating in bridged mode.

[6] It can be seen from the preceding sections that a bridged configuration of two amplifier channels delivers four times the power and doubles the dissipation.

This option is most often found in high power PA equipment or amplifiers designed for car audio applications.

Operation in parallel mode requires no special facility and is implemented merely by the appropriate external connection.

Stereo amplifiers usually have a common control for gain and frequently bass/treble and when switched to bridge mode will automatically track each channel identically.