| 摘要 |
<p>Fully programmable high precision filter having a filter input and a filter output including a first, first order low pass filter section comprising first and second mutually identical operational transconductance amplifiers (OTAs), each having a controllable transconductance Gm from a differential voltage input to a single current output, the current outputs of both first and second OTAs being resistorless coupled to a first capacitor, the second OTA being arranged to form a variable positive virtual resistance across said first capacitor, a gain and a bandwidth control signal being respectively supplied to said first and second OTA. To provide an unambiguous control of filter parameters, as well as flexibility in selectivity mode (i.e. bandpass or low pass filter mode) by means of programmable digital or analogue control signals with a performance comparable to programmable digital filters, a second order low pass filter section is being applied, comprising a cascade connection of said first, first order low pass filter section with an identical second, first order low pass filter section comprising a second capacitor, identical to the first capacitor, the first OTA thereof being varied in its transconductance with said gain control signal, the second OTA of both first and second, first order low pass filter sections being varied in their transconductances with said bandwidth control signal, an output terminal of the second, first order low pass filter section being fed back through a feedback OTA to the common connection between the output terminal of the first, first order low pass filter section and an input terminal of the second, first order low pass filter section, said feedback OTA being identical to each of the OTAs of the first and second first order low pass filter sections and being supplied with a feedback control signal through a feedback control signal terminal.</p> |
