A novel microprocessor-controlled active-R multifunction network: design of programmable filter, oscillator, and FSK/PSK wave generator

A two-operational amplifier (OA) active-R network with multifilter/oscillator functional capability is described. Analysis indicates the availability of bandpass (BP), low-pass (LP), band-reject (BR), all-pass (AP), and sinusoidal oscillator functions at extended frequency range with low sensitivity. Design equations and expressions for frequency stability and sensitivity are derived. Designs for both continuous and digitally programmable control of the network parameters using appropriate switched resistors have been derived and verified experimentally. The scanning of a typical band (50-200 kHz with mu A/LM 741 and 200-1000 kHz with LF 356 OAs) at certain programmable center frequencies has been verified experimentally while setting Q=10 with an appropriate resistor switching sequence generated by the microprocessor.<
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