Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1997-09-08
1999-01-19
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330 84, 330254, 330258, H03F 345, H03F 368, H03G 330
Patent
active
058617787
ABSTRACT:
A low noise amplifier structure based on a Differential Difference Amplifier (DDA1) having a differential output (outp, outn) and two differential pairs of input terminals (N1, P1; N2, P2). The input signal (V.sub.IN) is applied to terminals (N2, P1) which belong to different differential pairs. In this way, none of the differential pairs receives a high input signal, and hence none of them cause unacceptable harmonic distortion. The dynamic input range is thus high. The gain of the structure is determined by a resistive circuit (R2a, R2a'; R2b, R2b') coupled to the remaining terminals (N1, P2) of the differential pairs. The common mode of these remaining terminals (N1, P2) is, independently from the output common mode, biased at the input common mode via a common mode feedback circuit (DDA2; GL1, GH1, GH3, R2a, R2a'; GL2, GH2, GH4, R2b, R2b') based on a second differential difference amplifier (DDA2). Some switching elements (GL1, GH1, GH3; GL2, GH2, GH4) allow the gain to be programmed and prevent the common mode feedback circuit from injecting differential noise if the gain is high. The structure is adapted to amplify signals of 1 Vpp with acceptably low distortion.
REFERENCES:
patent: 5327098 (1994-07-01), Molina et al.
patent: 5339285 (1994-08-01), Straw
"A 3.3-V 800-n V.sub.rms Noise, Gain -Programmable CMOS Microphone Preamplifier Designs Using Yield Modeling Technique", G. Nicollini et al, IEEE Journal of Solid-State Circuits, vol. 28, No. 8, Aug. 1993, pp. 915-921.
"A Versatile Building Block: The CMOS Differential Difference Amplifier", E. Sackinger et al, IEEE Journal of Solid-State Circuits, vol. SC-22, No. 2, Apr. 1987, pp. 287-294.
Cornil Jean-Philippe Robert
Louagie Filip Marcel
Alcatel Alsthom Compagnie Generale d'Electricite
Mullins James B.
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