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US 4,375,038 AGranted
RMS Converter
AssigneeBeckman Instruments, Inc.
InventorJohn B. Crosby
Life of this patent
Estimating the term…
Abstract
A circuit for measuring the root-mean-square (RMS) value of an electrical signal. The output may be linear or logarithmic. The circuit uses devices with logarithmic voltage/ current characteristics (usually transistors), and allows the logarithmic devices to be connected directly together without intervening operational amplifiers. In its simplest form, the invention consists of a rectifier circuit, four transistors and a capacitor.
Claims13
An electrical circuit which provides a unidirectional output current whose average value is proportional to the root-mean-square (RMS) value of a time-varying input signal, comprising
- an output terminal out of which flows the output current;
- a common node;
- a rectifying circuit, adapted for receiving the input signal, which includes a current node and which produces a unidirectional current flowing out of the current node whose value is proportional to the absolute value of the input signal;
- a voltage source terminal, adapted for connection to a voltage source;
- a first transistor whose collector connects to the voltage source terminal and whose base connects to the current node;
- a second transistor whose collector connects to the current node and whose base connects to the emitter of the first transistor;
- a first semiconductor rectifier connected between the emitter of the second transistor and the common node;
- a third transistor whose collector connects to the output terminal and whose base connects to the base of the second transistor;
- a second semiconductor rectifier connected between the emitter of the third transistor and the common node;
- and
- a capacitor connected to, and in parallel with, the second semiconductor rectifier.
8 more elements
An electrical circuit which provides an output voltage proportional to the logarithm of a quantity proportional to the root-mean-square (RMS) value of a time-varying input signal, comprising
- a first output terminal and a second output terminal, across which appears the output voltage;
- a voltage source terminal, adapted for connection to a voltage source;
- a rectifying circuit, adapted for receiving the input signal, which includes a current node and which produces a unidirectional current flowing out of the current node whose value is proportional to the absolute value of the input signal;
- two semiconductor rectifiers connected in a series circuit, this series circuit being connected between the current node of the rectifying means and the first output terminal;
- a transistor whose collector connects to the voltage source terminal, whose base connects to the current node of the rectifying means, and whose emitter connects to the second output terminal;
- a third semiconductor rectifier connected between the first output terminal and the second output terminal;
- and
- a capacitor connected between the first output terminal and the second output terminal.
5 more elements
An electrical circuit which provides an output voltage proportional to the logarithm of a quantity proportional to the root-mean-square (RMS) value of a time-varying input signal, comprising
- a voltage source terminal, adapted for connection to a voltage source;
- a rectifying circuit, adapted for receiving the input signal, which includes a current node and which produces a unidirectional current flowing out of the current node whose value is proportional to the absolute value of the input signal;
- a first transistor whose collector connects to the voltage source terminal and whose base connects to the current node of the rectifying circuit;
- a second transistor whose collector and base connect to the base and emitter, respectively, of the first transistor;
- a common node;
- a first semiconductor rectifier connected between the emitter of the second transistor and the common node;
- a first output terminal and a second output terminal, across which appears the output voltage, the second output terminal being connected to either the common node or the emitter of the first transistor;
- a capacitor connected between the first output terminal and the second output terminal;
- a second semiconductor rectifier connected between the first output terminal and the common node;
- and
- a third semiconductor rectifier connected between the emitter of the first transistor and the first output terminal.
8 more elements
An electrical circuit which provides an output voltage proportional to the logarithm of a quantity proportional to the root-mean-square (RMS) value of a time-varying input signal, comprising
- a voltage source terminal, adapted for connection to a voltage source;
- a rectifying circuit, adapted for receiving the input signal, which includes a current node and which produces a unidirectional current flowing out of the current node whose value is proportional to the absolute value of the input signal;
- a first transistor whose collector connects to the voltage source terminal and whose base connects to the current node of the rectifying circuit;
- a second transistor whose collector and base connect to the base and emitter, respectively, of the first transistor;
- a first output terminal and a second output terminal, across which appears the output voltage;
- a capacitor connected between the first output terminal and the second output terminal;
- a first semiconductor rectifier connected between the emitter of the second transistor and the second output terminal;
- a second semiconductor rectifier connected between the first output terminal and the second output terminal;
- and
- a third transistor whose collector connects to the voltage source terminal, whose base connects to the emitter of the first transistor, and whose emitter connects to the first output terminal.
7 more elements
An electrical circuit which provides a unidirectional output current whose average value is proportional to the root-mean-square (RMS) value of a time-varying input signal, comprising
- an output terminal out of which flows the output current;
- a common node;
- a rectifying circuit, adapted for receiving the input signal, which includes a current node and which produces a unidirectional current flowing out of the current node whose value is proportional to the absolute value of the input signal;
- a voltage source terminal, adapted for connection to a voltage source;
- transistor means having first and second main path terminals and a control terminal, wherein the first main path terminal connects to the voltage source terminal and the control terminal connects to the current node;
- a first transistor whose collector connects to the current node and whose base connects to the second main path terminal of the transistor means;
- a first semiconductor rectifier connected between the emitter of the first transistor and the common node;
- a second transistor whose collector connects to the output terminal and whose base connects to the base of the first transistor;
- a second semiconductor rectifier connected between the emitter of the second transistor and the common node;
- and
- a capacitor connected to, and in parallel with, the second semiconductor rectifier.
8 more elements
An electrical circuit which provides an output voltage proportional to the logarithm of a quantity proportional to the root-mean-square (RMS) value of a time-varying input signal, comprising
- a voltage source terminal, adapted for connection to a voltage source;
- a rectifying circuit, adapted for receiving the input signal, which includes a current node and which produces a unidirectional current flowing out of the current node whose value is proportional to the absolute value of the input signal;
- transistor means having first and second main path terminals and a control terminal, wherein the first main path terminal connects to the voltage source terminal and the control terminal connects to the current node of the rectifying circuit;
- a transistor whose collector and base connect to the control terminal and second main path terminal, respectively, of the transistor means;
- a common node;
- a first semiconductor rectifier connected between the emitter of the transistor and the common node;
- a first output terminal and a second output terminal, across which appears the output voltage, the second output terminal being connected to either the common node or the second main path terminal of the transistor means;
- a capacitor connected between the first output terminal and the second output terminal;
- a second semiconductor rectifier connected between the first output terminal and the common node;
- and
- a third semiconductor rectifier connected between the second main path terminal of the transistor means and the first output terminal.
8 more elements
Dependencies are inferred from the claim text.