Abstract A logarithmic converter circuit comprising an emitter-coupled pair of transistors and a pair of operational amplifiers is provided with a temperature-stabilized environment so that accurate logarithmic conversion is facilitated. One of the pair of transistors is utilized as a temperature sensor to provide a temperature control voltage, which in turn controls the power applied to a heating element disposed adjacent the pair of transistors to maintain a constant semiconductor junction temperature. The heating element may suitably be one or more transistors disposed proximate the pair of transistors on a common substrate. The absolute temperature of the sensor transistor base-to-emitter junction is established by the use of precise gain-setting components, and by adjusting the temperature reference voltage for the correct system gain.
Inventors
👤 Rush W. Hood, Jr.
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-25 18:58
CPC Classifications
G; G06; G06G; G06G7/00; G06G7/12; G06G7/24
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
115 words
A temperature-stabilized logarithmic converter circuit, comprising: an emitter coupled pair of transistors; first and second operational amplifiers operatively associated with said pair of transistors in such a manner that at least a portion of each transistor forms part of the feedback loop for a respective operational amplifier, whereby a voltage at the output of said first operational amplifier is logarithmically related to a voltage at the input thereof; means for heating said pair of transistors to a temperature higher than ambient; means for sensing a change in the junction temperature of one of said pair of transistors; and heater control means responsive to said sensing means for controlling the power applied to said heating means.
Claim 2
Dependent Claim
115 words
A temperature-stabilized logarithmic converter circuit, comprising: an emitter coupled pair of transistors; first and second operational amplifiers operatively associated with said pair of transistors in such a manner that at least a portion of each transistor forms part of the feedback loop for a respective operational amplifier, whereby a voltage at the output of said first operational amplifier is logarithmically related to a voltage at the input thereof; means for heating said pair of transistors to a temperature higher than ambient; means for sensing a change in the junction temperature of one of said pair of transistors; and heater control means responsive to said sensing means for controlling the power applied to said heating means.
Claim 3
Dependent Claim
22 words
A circuit in accordance with claim 1 wherein said heating means comprises at least one transistor disposed adjacent said pair of transistors.
Claim 4
Dependent Claim
20 words
A circuit in accordance with claim 2 wherein said pair of transistors and said heating transistor share a common substrate.
Claim 5
Dependent Claim
44 words
A circuit in accordance with claim 1 wherein said sensing means comprises means for operating said one of said pair of transistors at a constant current and constant collector and base voltages, and means for comparing the emitter voltage thereof with a reference voltage.
Claim 6
Dependent Claim
29 words
A circuit in accordance with claim 1 wherein said heater control means comprises an amplifier responsive to said sensing means, and a variable current source responsive to said amplifier.