Modified Current-mode CCII-Based Multifunction Biquadratic Filter

The filter is a kind of dual-port frequency selective network structured the interconnection of electric components. As a science, it has already had a history of more than 90 years up to now. Today, besides large amount of application in communication field, it has also been widely applied in control, radar, satellite, instrument and computer fields.In recent several years, the electrical equipments and instruments approach to small type and mini type, the development trend of analog integrated filter is low-voltage, low-power consumption as well as high-working frequency and large dynamics range, which is the development direction of modern active filter. With the development of analog integrated technology, the defects of voltage mode design have been exposed one by one:(1) As the signal carrier, the interval voltage of nonlinear devices for analog signal processing is greatly affected by the temperature and it is difficult to ensure the working accuracy under the situation of high integration.(2) The working frequency bands of voltage mode devices are relatively narrow.(3) Due to the limitation of analog integration technology, it is difficult to improve the signal processing speed of voltage mode.What is called current mode circuit is the circuit taking current as the parameter of analog signal processing. Both input and output signals are current. The circuit without other voltage parameters except crystal triode junction voltage in whole circuit is strictly called current mode circuit, which has following several merits:(1) Low input impedance and high output impedance.(2) Large dynamic range and low power consumption.