An improved OBT strategy for catastrophic faults detection in continuous-time analog filters

Usually in analog filters, the dispersion of process parameters is corrected by means of tuning circuitry, normally built-in with the filter. In such a case, the classical OBT can be used for fault detection. When the filter is not self-tuned however, the OBT oscillation frequency may differ considerably from its nominal expected value due to the parameter dispersion. This could lead to diagnosing a device as faulty when it is indeed sound but out of tune. This paper presents a novel OBT (Oscillation Based Test) scheme applied to a Gm-C band-pass filter without tuning capability, taken here as a case study. It is based on the relative comparison of two oscillation frequencies. A proof of concept is given through simulations carried out on a 2
^nd
order band-pass filter that has been adopted as a case study.