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Op-amp Bridge Drive

    This circuit is composed of two op-amps. One is configured as a non-inverting amplifier and the other is configured as an inverting amplifier. The load is driven by connecting it between the two outputs.

Schematic diagram of a bridge drive op-amp circuit.

    In this configuration, when Vin is positive the non-inverting op-amp’s output will be positive and inverting op-amps output will be negative. The voltage across the load is double that of a single op-amp driving a load to ground. When Vin goes negative, the polarity of the outputs switches putting twice the voltage across the load in the opposite polarity. From the loads perspective it is seeing twice the peak to peak voltage than it see from a single op-amp. Assuming the op-amp was operating on ±15V supplies and capable of driving to ±13.5V, the load would see an equivalent peak to peak voltage of 54V.

    The circuit gain can be set by using the non-inverting solver to find R1 and R2. R3 and R4 should be of equal value so that the inverting amplifier tracks the output of U1. R5 is used to minimize the DC offset and should be equal to R3 in parallel with R4. R5 can be omitted if desired by connecting U2's non-inverting input to ground.

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