Miscellaneous active electrical nonlinear devices – circuits – and – Specific input to output function – Logarithmic
Patent
1993-10-22
1995-09-19
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific input to output function
Logarithmic
327350, 327362, 330279, G06F 7556
Patent
active
054518954
ABSTRACT:
A wideband amplifier which employs a plurality of cascaded logarithmic amplifier stages under the control of a digital signal processor which nulls offset voltages. In one aspect of the invention, the digital signal processor controls switches, one switch associated with each amplifier stage for determining an appropriate offset voltage and producing a counterbalancing signal. In another aspect of the invention the amplifier includes two potentiometers or variable signal devices which can set the overall input signal level and set the ratio of maximum to minimum of the input signal level, respectively, to desired levels. In a third aspect of the invention, a lookup table is associated with the digital signal processor for storing correction factors to be applied to digitized values in order to produce a final result which is corrected for variations in the amplifier characteristic from true logarithmic.
REFERENCES:
patent: 4990803 (1991-02-01), Gilbert
patent: 5077541 (1991-12-01), Gilbert
patent: 5216384 (1993-06-01), Vanhecke
Analog Devices, "Dual, Low Noise, Wideband Variable Gain Amplifiers AD600/AD602", Rev.0 (1992).
Callahan Timothy P.
Lumisys Inc.
Zweizig Jeffrey
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