Marina Santo Zarnik, Franc Novak, Srecko Macek, Efficient go no-go test of active RC filters,
Int. Journal of circuit theory and applications, Vol.26, 1998, pp. 523-529

Test generation techniques of analogue circuits have been studied for more than two decades followed by the development of the corresponding design-for-testability (DFT) techniques. The requirements for fast, efficient and low-cost testing impose solutions suitable for specific classes of circuits. Hence general test strategies are usually further developed to achieve partial solutions suitable for specific classes of circuits.

An oscillation-based test approach has recently been applied to testing integrated operational amplifiers and digitally-programmable switched-current biquadratic filters. In oscillation-based testing, the unit-under-test is converted to an oscillating circuit and the frequency of oscillation is measured. Changes of the frequency of oscillation from its nominal value indicate possible faults in the unit-under-test. The method of putting the unit-under-test in the oscillation mode and the choice of the actual frequency of oscillation are specific for the fault detection procedure employed.

In this paper we propose an oscillation-based test structure for testing active RC filters. For this class of circuits, different DFT methodologies have been reported after the initial work of M.Soma. Our approach can be regarded as complementary to the existing methodologies since it is primarily used as an effective go no-go test that verifies if the filter-stage-under-test conforms with the required specifications.

The proposed test structure uses an all-pass equalizer in order to fulfil the conditions for oscillation at the frequency of the pole of the filter stage-under-test. Examples of testing a bandpass resonator active filter and a low-pass filter stage with a frequency dependent negative resistor (FDNR) are presented to illustrate the approach.