TABLE OF CONTENTS Like the op-amps, also CCIIs can be utilized in the design of analog filters, especially the current-mode ones. In the following, we will consider both passive and active filter implementation through current conveyers. In the previous section a CCII-based capacitance multiplier has been introduced. The simplest application of this circuit, related to analog filters, is represented by a RC filter. Connecting a resistance to the input terminal of the capacitance multiplier previously described, as shown in figure 5.31, a low pass filter is obtained [16], [17].
Using a 100 K ? resistance, a 50 pF capacitance and imposing a current gain of 50,000, it is possible to implement a low pass filter having very low cut-off frequencies (for example, lower than 1 Hz), as shown in figure 5.32. The advantage of this solution is represented by its intrinsic simplicity and by the fact that it is suitable for fully integrated implementation.
The high valued inductances and capacitors, designed in the previous sections, can be employed in the implementation of a fully integrable LC band-pass filter, whose resonating frequency is equal, as well known, to:
From eq. (5.28), it comes that low resonating frequencies can be obtained only if high values for both capacitors and inductors are employed. In order to show how the proposed circuits can be applied for the implementation of a LC band pass filter, three different topologies, reported in...
