Define roll of rate and order of filter.
1. Roll of rate is the rate of change of gain with frequency. Roll of rate is always measured in dB/decade.
2. The roll of rate is called the order of the filter.
It depends on the rate at which filter‟s gain changes with frequency.
For example:
i) If roll off rate is -20 dB / decade or +20 dB / decade then the filter is of 1st order.
ii) If roll of rate is -40 dB / decade or +40 db / decade then the filter is of 2nd order and so on