Design of a new high order OTA-C filter structure and its specification based testing

This paper presents a new higher order current mode filter structure based on Operational transconductance amplifier and capacitor (OTA-C). The structure fulfils the three main criteria of high frequency operation: (i) It employs minimum number of active and passive components (ii) It employs only single ended input OTAs to overcome feedthrough effects. (iii) It uses only grounded capacitor which is useful for integration and absorb shunt capacitance. Any nth order transfer function can be realised from it. Fourth order low pass elliptic filter is designed and simulated. HSPICE simulation with BSIM level 53 model and 0.13 μm process confirm the theoretical analysis. The second part of the paper proposes a new method of specification based parametric fault detection of higher order linear analog circuit where a number of test nodes are accessible. The method is illustrated with designed fourth order low pass elliptic filter. Current gains at different stage of the filter are used for fault detection. Using montecarlo simulation the value of each component of the circuit is varied within its tolerance limit and minimum and maximum values of the each current gain are found for the fault free circuit. At the time of testing, the current gains are found for the injected fault and if any one or more current gain are found out of bound then the circuit is faulty. Numerical results are presented to clarify the proposed method and to prove its efficiency.