Continuous-time high-frequency active filters suitable for monolithic implementation by standard low cost bipolar process are presented. Balanced NIC's are used to cancel out the loss of passive RC integrators, thus realizing active loss-less integrators with good high-frequency performance. Two types of balanced integrators are proposed and their quality factors are analyzed. The proposed NIC-integrators are used to realize tunable active filters capable of low-voltage operation and without the drawbacks of the NIC-gyrator filters. As an example of application of the NIC-integrators to leapfrog simulation of RLC ladders a second-order 1 MHz bandpass filter was designed, computer simulated and laboratory tested showing good results.

Electronic circuits operating from low-voltage power supplies are required in battery operated equipments and in monolithic ICs realized using high-frequency high-density integrated circuit technology. High-frequency active filters that are suited for monolithic implementation using integrators based on negative impedance converters (NICs) have been presented in the literature. In this paper a low-voltage NIC-integrator is presented along with some applications to high-order high-frequency active filters. Methods to compensate the losses of integrators suitable for high-frequency low-power applications are introduced. Realizations of high-order filters with transmission zeros without floating capacitors or additional summers are also presented. Experimental and simulation results are shown to confirm the validity of the proposed circuits.