Performance enhancement induced Trojan states in op-amps, their detection and removal

It is well-known that self-stabilized circuits, such as current, voltage and frequency references, are vulnerable to multiple operating points problem. This is also known as the start-up problem. In this paper, we show that the widely used analog building block, namely the op-amp, can suffer from the same problem when performance enhancement feedback is being used. In particular, slew rate enhancement circuit (SRE) can be used as an performance enhancement circuitry in the low power high speed op-amp design. For such circuit, we present a systematic method for detecting and removing Trojan state. With design example and simulation results, it is demonstrated that the proposed method can effectively remove Trojan state in the op-amp.