Active filter circuit using simulated inductance - is provided by switched capacitors and operational amplifier and allows simultaneous signal transfer in both directions

摘要

The circuit uses controlled switches (S13,S16,S23) capacitors (14,15,16) and an operational amplifier (10), with a feedback capacitor (14) between its output (13) and its inverting input (11), the non-inverting input (12) being earthed. The inverting input (11) of the operational amplifier (10) is coupled via a switch (S13) to a node point (19) connected to earth via a capcitor (16) and to a second node point (20) by a second switch (S14). This node point (20) is also connected to earth via a capacitor (15) and to the inverting input (11) of the operational amplifier (10) and to its output (13), via two further switches. A final switch (S23) couples the second node point (20) to the circuit input (17), the first and final switches (S13,S23) are closed simultaneously and the remaining switches (S14,S15,S16) are closed one after the other.