Design of a Tunable Active Low Pass Filter by CMOS OTA and a Comparative Study with NMOS OTA with Different Current Mirror Loads

The operational amplifiers (OPAMP) are basic building blocks in implementing a variety of analog circuits such as amplifiers, filters, integrators, differentiators, summers, oscillators etc. OPAMPs work well for lowfrequency applications, such as audio and video systems. For higher frequencies, however, OPAMP designs become difficult due to their frequency limit. At those high frequencies, operational transconductance amplifiers (OTAs) are deemed to be promising to replace OPAMPS as the building blocks. This paper illustrates an application of OTA as an active low pass filter. The primary building block of an OTA is the current mirror. In this paper different current mirrors are used to design the LPF & the corresponding frequency and phase responses are comparatively studied. Also a comparative study of CMOS OTA & NMOS OTA is also illustrated in this paper. Finally, the applications of OTA based LPF are also studied. 