Electronic tunability in analog filters

Abstract

In the beginning years of the analog design, discrete components were being used in the analog design procedures. After manufacturing, trimmer capacitors and potentiometers were used for electronic tunability to compensate for the electronic component nonidealities and tolerances. After 1970s, analog circuits have been implemented as integrated circuits, where element tolerances are unacceptably high. Non-idealities and parasitics due to IC implementation are serious problems for the circuits after manufacturing. Therefore, electronic tuning of some parameters after production has been a very important feature in IC design. In the thesis following major tunability methods are examined: Electronic tunability with MOSFET-C technique, with mixed translinear loops, with operational transconductance amplifiers and with adjusting current-gain. During electronic tuning of the desired parameters, some other parameters of the circuit such as linearity, stability, gain and high frequency performance, may be affected in an undesired way. Therefore, trade-offs between tunability and other parameters of the circuits are illustrated to find effective tunability ranges. Moreover, in the thesis new tunable filter circuits are suggested for each of these methods as examples and detailed non-ideality and parasitic component analyses of these circuits are given.