A new BIST technique for embedded operational amplifiers in mixed-signal circuits is presented in this paper. The technique is based on the detection of the slew-rate deviation, which is a sensitive parameter to defects. The BIST circuitry requires a small area overhead. It is compatible with digital parts since it uses only logic gates, and generates a One-Bit-Signature (OBS), which offers a good observability of the test response. In order to validate the proposed BIST technique, an Op Amp circuit has been considered as test vehicle. Simulation results show that the proposed technique offers a high fault coverage.