US Patent 8710847 Self-correcting amplifier system

DC offsets introduced in battery testing equipment are automatically compensated for using complementary current-mode servo feedback. An op amp receives and amplifies a response signal, while also introducing internal errors manifested in the amplified response signal. A correction circuitry coupled to receive the amplified response signal and comprising a balanced circuit with a positive input correction device and a negative input correction device to remove the DC bias. The correction circuitry further comprises an error sensing device to correct for the internal errors introduced by the op amp.