US3700918A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Logarithmic amplifier
Assignee: Mitsubishi Electric Corp
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Filing: 1970-04-13
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Granted: 1972-10-24
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Expires: 1990-04-13
Abstract
Abstract A circuit including a semiconductor logarithmic transfer element is connected to an operational amplifier through a resistor having a resistance proportional to its absolute temperature. A comparison voltage dependent upon the transfer element is also applied to the amplifier through another resistor similar in temperature dependency to the first resistor to be substracted from the output from the circuit. The resulting difference is completely temperature compensated and indicated on an indicator having an indication span controlled by a variable resistor connected across the amplifier and a zero point adjusted by a bias to the amplifier.
Inventors
- 👤 Katsuhiko Kawashima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 18:01
CPC Classifications
G; G06; G06G; G06G7/00; G06G7/12; G06G7/24
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
136 words
A logarithmic amplifier having an improved temperature compensation characteristic comprising, in combination, a logarithmic transfer circuit having an input for receiving an input signal voltage, having an output, and including a semiconductor logarithmic transfer element, a voltage generator circuit for generating a predetermined voltage at an output thereof, and an analog operational amplifier circuit having first and second inputs coupled respectively to said logarithmic transfer circuit and said voltage generator circuit outputs, said analog operational amplifier circuit including means for varying the gain of said analog circuit in a relation inversely proportional to the absolute temperature of said gain varying means, and including means for producing an output voltage equal to the difference between an output voltage from said logarithmic transfer circuit and said predetermined voltage from said voltage generator circuit, multiplied by said gain thereof.
Claim 2
Dependent Claim
136 words
A logarithmic amplifier having an improved temperature compensation characteristic comprising, in combination, a logarithmic transfer circuit having an input for receiving an input signal voltage, having an output, and including a semiconductor logarithmic transfer element, a voltage generator circuit for generating a predetermined voltage at an output thereof, and an analog operational amplifier circuit having first and second inputs coupled respectively to said logarithmic transfer circuit and said voltage generator circuit outputs, said analog operational amplifier circuit including means for varying the gain of said analog circuit in a relation inversely proportional to the absolute temperature of said gain varying means, and including means for producing an output voltage equal to the difference between an output voltage from said logarithmic transfer circuit and said predetermined voltage from said voltage generator circuit, multiplied by said gain thereof.
Claim 3
Dependent Claim
28 words
A logarithmic amplifier as claimed in claim 1 wherein said gain varying means includes a resistor having a resistance value which varies in proportion to its absolute temperature.
Claim 4
Dependent Claim
42 words
A logarithmic amplifier as claimed in claim 1 wherein said gain varying means comprises a composIte resistor including a wire-wound resistor having resistance which varies in proportion to its absolute temperature, and a second resistor having a low temperature coefficient of resistance.
Claim 5
Dependent Claim
226 words
A logarithmic amplifier having an improved temperature compensation characteristic comprising, in combination, logarithmic transfer circuit means including a semiconductor logarithmic transfer element and having an input for receiving a direct current input signal, and an output for producing a signal which is a function of the logarithm of the received signal; voltage generator circuit means having an output for generating a predetermined voltage Uo dependent upon the geometry and material of said semi-conductor logarithmic transfer element and expressed by the equation Uo Vo + d(kTo/q, where Vo is an extrapolated energy gap when the semiconductor logarithmic transfer element is at O*K, d is a constant determined by the material of the semiconductor logarithmic transfer element, k is Boltzmann''s constant, To is a fixed temperature in *K selected from a temperature range over which the logarithmic amplifier is to be operated, and q is the elementary charge of said element; and an analog operational amplifier circuit having a gain inversely proportional to the absolute temperature thereof and including a pair of inputs connected respectively to said logarithmic transfer circuit means output and said voltage generator circuit means output, said analog operational amplifier including means for producing an output voltage equal to the difference between the output signal from said logarithmic transfer circuit means and said predetermined voltage from said voltage generator circuit means multiplied by said gain.
Claim 6
Dependent Claim
226 words
A logarithmic amplifier having an improved temperature compensation characteristic comprising, in combination, logarithmic transfer circuit means including a semiconductor logarithmic transfer element and having an input for receiving a direct current input signal, and an output for producing a signal which is a function of the logarithm of the received signal; voltage generator circuit means having an output for generating a predetermined voltage Uo dependent upon the geometry and material of said semi-conductor logarithmic transfer element and expressed by the equation Uo Vo + d(kTo/q, where Vo is an extrapolated energy gap when the semiconductor logarithmic transfer element is at O*K, d is a constant determined by the material of the semiconductor logarithmic transfer element, k is Boltzmann''s constant, To is a fixed temperature in *K selected from a temperature range over which the logarithmic amplifier is to be operated, and q is the elementary charge of said element; and an analog operational amplifier circuit having a gain inversely proportional to the absolute temperature thereof and including a pair of inputs connected respectively to said logarithmic transfer circuit means output and said voltage generator circuit means output, said analog operational amplifier including means for producing an output voltage equal to the difference between the output signal from said logarithmic transfer circuit means and said predetermined voltage from said voltage generator circuit means multiplied by said gain.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-24 | 1976-04-24 | 1976-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-24 | 1980-04-24 | 1980-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-24 | 1984-04-24 | 1984-10-24 | $7700.00 | Window Closed / Lapsed |