Amplifiers – Signal feedback – Frequency responsive feedback means
Patent
1980-06-06
1983-08-16
Larkins, William D.
Amplifiers
Signal feedback
Frequency responsive feedback means
330306, 333172, 357 14, 357 23, 357 51, 357 59, H01L 2994, H01L 2704, H03H 701
Patent
active
043994172
ABSTRACT:
A capacitor-resistor-capacitor (CRC) element for active filter realization, which is fully integrable and compatible with MOS technology, is described. The incorporation of the CRC element in a semiconductor integrated circuit active filter also is described. The structure of the CRC filter element is closely analogous to a depletion mode MOS field effect device, except that the channel zone 26 is doped to a level which substantially precludes conductivity modulation at the usual operating voltages. However, the doping level is such as to enable the use of the channel zone as a semiconductor resistance element. Thus, the N-channel CRC element realized in the NMOS technology comprises a first capacitance composed of the gate 27, gate dielectric 38, and resistive channel 26, paralleled by the resistive channel 26 itself constituting a resistor, and then the underlying PN junction capacitance between the N-type resistive channel 26 and the underlying P-type semiconductor body portion 21. An active low-pass filter consists of two CRC elements and an operational amplifier and utilizes the positive feedback principle.
REFERENCES:
patent: 3953875 (1976-04-01), Cave et al.
patent: 4092619 (1978-05-01), Huggins
patent: 4143387 (1979-03-01), Stikvoort
patent: 4233615 (1980-11-01), Takemoto et al.
patent: 4285001 (1981-08-01), Gerzberg et al.
Gray et al., IEEE J. of Solid State Circuits, vol. SC14, No. 6, Dec. 1979, pp. 981-990.
Ballantyne James P.
Fleischer Paul E.
Laker Kenneth R.
Yiannoulos Aristides A.
Bell Telephone Laboratories Incorporated
Larkins William D.
Lockhart H. W.
Torsiglieri Arthur J.
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