US3624409A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Logarithmic converter
Assignee: HP Inc
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Filing: 1970-09-03
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Granted: 1971-11-30
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Expires: 1990-09-03
Abstract
Abstract A logarithmic converter which includes a differential amplifier with one input connected to a logarithmic transfer circuit and another input connected to a temperature compensating reference circuit for producing an output signal from the differential amplifier that is proportional to the logarithm of the ratio of a signal applied to the input of the logarithmic transfer circuit and a reference signal. The logarithmic transfer circuit includes a gain-inverting amplifier having a transistor connected in a feedback arrangement. Resistive elements are connected between the signal input connection, the transistor and a reference potential to improve the linearity of the transfer characteristic.
Inventors
- 👤 Jerry B Folsom
- 👤 Robert E Hetzel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:58
CPC Classifications
G; G06; G06G; G06G7/00; G06G7/12; G06G7/24
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
144 words
Apparatus for producing an output signal proportional to the logarithm of the ratio of an applied input signal to a reference signal, the apparatus comprising: a gain-inverting amplifier having an output and having an input; a logging transistor having a base, an emitter connected to the output of said gain-inverting amplifier and a collector connected to the input of said gain-inverting amplifier; an input terminal for receiving input signals; a first resistive means connected between said input terminal and the input of said gain-inverting amplifier; and a second and third resistive means, said second resistive means connected between said input terminal and the base of said logging transistor, said third resistive means connected between the base of said logging transistor and a source of reference potential for biasing said logging transistor in response to the magnitude of a signal applied at said input terminal.
Claim 2
Dependent Claim
144 words
Apparatus for producing an output signal proportional to the logarithm of the ratio of an applied input signal to a reference signal, the apparatus comprising: a gain-inverting amplifier having an output and having an input; a logging transistor having a base, an emitter connected to the output of said gain-inverting amplifier and a collector connected to the input of said gain-inverting amplifier; an input terminal for receiving input signals; a first resistive means connected between said input terminal and the input of said gain-inverting amplifier; and a second and third resistive means, said second resistive means connected between said input terminal and the base of said logging transistor, said third resistive means connected between the base of said logging transistor and a source of reference potential for biasing said logging transistor in response to the magnitude of a signal applied at said input terminal.
Claim 3
Dependent Claim
115 words
Apparatus as in claim 1 and including: a reference transistor having similar characteristics to those of said logging transistor, having an emitter and having a base and a collector connected to a common source of reference potential for maintaining a zero bias between collector and base; a voltage supply connected to the emitter of said reference transistor for producing a forward bias on the emitter-base junction; a differencing means having an input to receive signals from said gain-inverting amplifier and from said reference transistor and having an output for producing signals which are proportional to the difference between input signals; and means to maintain the logging transistor and the reference transistor at a constant temperature.
References Cited (Backward Citations)
US3524074A
Cited
US3506847A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-29 | 1975-05-31 | 1975-11-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-29 | 1979-05-31 | 1979-11-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-29 | 1983-05-31 | 1983-11-30 | $7700.00 | Window Closed / Lapsed |