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US 5,471,173 AGranted
Cascaded amplifier having temperature compensation
AssigneeU.S. Philips Corporation
InventorsPaul A. Moore, Anthony R. Cusdin
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AssigneeU.S. Philips Corporation
InventorsPaul A. Moore, Anthony R. Cusdin
Estimating the term…
A cascaded amplifier is comprised of a number of amplifying stages connected in cascade such as the dual emitter-coupled amplifier shown. A first pair of transistors (14,20) provides limiting amplification and a second pair of transistors (16,18) with degeneration (22,24) provide linear amplification. Each pair of transistors is driven by a current source (28,26) which supplies a current (IT, IT2) proportional to absolute temperature (PTAT). The small signal amplification is then substantially independent of temperature and the value of the limited output is proportional to absolute temperature. This latter effect is countered by including a translinear variable current gain amplifier (54,56,58,60) in the last dual-gain stage of the cascaded amplifier to modify the output voltage in a manner inversely proportional to absolute temperature. A transfer function may thus be provided which is substantially independent of temperature.
A cascaded amplifier comprising a plurality of amplifying stages coupled in cascade, each amplifying stage comprising a linear amplifier and a limiting amplifier, the linear amplifier and the limiting amplifier being provided with a stage input signal and providing respective output signals which are combined to provide a stage output signal, wherein each amplifying stage in the cascade further comprises a temperature dependent device for controlling the small signal gain of that amplifying stage to be substantially independent of temperature and a final stage of the amplifier comprises an overall temperature dependent device for controlling the overall output limit voltage of the cascaded amplifier to be substantially independent of temperature.
A radio receiver comprising a radio frequency state including frequency down-conversion means for providing a down converted signal to a logarithmic amplifier including a plurality of amplifying stages coupled in cascade, each amplifying stage comprising a linear amplifier and a limiting amplifier, wherein the linear amplifier of each amplifying stage is arranged to have a gain of unity and the logarithmic amplifier provides a substantially logarithmic transfer function, the linear amplifier and the limiting amplifier being provided with a stage input signal and providing respective output signals which are combined to provide a stage output signal, wherein each amplifying stage in the cascade further comprises a temperature dependent device for controlling the small signal gain of that amplifying stage to be substantially independent of temperature and a final stage of the logarithmic amplifier comprises an overall temperature dependent device for controlling the overall output limit voltage of the cascaded amplifier to be substantially independent of temperature and wherein an output of the logarithmic amplifier is substantially logarithmically related to the down-converted signal being provided to a digitizing device to provide a digital signal to a digital signal processor.
A logarithmic amplifier having an input and an output which provides an output signal which retains information about the sign of an input signal, comprising:
Dependencies are inferred from the claim text.