JPH04282909A - Logarithmic amplifier - Google Patents

Abstract

PURPOSE:To eliminate a distortion from a synthesis point and to expand the dynamic range by synthesizing a 1st logarithmic amplifier signal obtained by logarithmically amplifying an input signal and a 2nd logarithmic amplifier signal obtained by attenuating and logarithmically amplifying the input signal at a linear region. CONSTITUTION:A logarithmic amplifier 21 of a logarithmic amplifier circuit 20 applies logarithmic amplification to an input signal and outputs a signal VO1 to a changeover switch 23. The signal VO1 is outputted to an output terminal 12 through the switch 23 when the signal VO1 is less than a setting signal VR1 of a setting device 22. Then an attenuator 31 of a logarithmic amplifier circuit 30 attenuates an input signal V1 properly, logarithmic amplification is implemented and a signal VO2 is outputted to a comparator 34. When the signal VO2 is larger than a setting signal VR2 of a setting device 33, the signal VO2 is outputted to a terminal 12 through a diode 35. Thus, the logarithmic amplifier signals VO1, VO2 of the circuits 20, 30 are synthesized at a linear region and the result is outputted from the terminal 12. Thus, distortion is eliminated from the signal synthesis point and the dynamic range is expanded.

Description

[Detailed description of the invention]

0001

[Purpose of the invention]

0002

[Field of Industrial Application] The present invention relates to a logarithmic amplification device.
In particular, the first logarithmically amplified signal obtained by logarithmically amplifying the input signal applied to the input terminal in the first logarithmically amplifying circuit and the second logarithmically amplified signal
The input signal applied to the input terminal is suitably attenuated by the logarithmic amplifier circuit, and then the second logarithmically amplified signal obtained by logarithmically amplifying the signal is combined in a linear region, or the first logarithmically amplifying circuit A first logarithmically amplified signal obtained by appropriately amplifying the input signal applied to the input terminal and then logarithmically amplifying the signal, and a logarithmically amplifying signal obtained by logarithmically amplifying the input signal applied to the input terminal in a second logarithmically amplifying circuit. This invention relates to a logarithmic amplification device in which the dynamic range is expanded by combining the obtained second logarithmically amplified signal in a linear region.

0003

[Prior Art] Conventionally, this type of logarithmic amplifier has
The first logarithmically amplified signal obtained by logarithmically amplifying the input signal by the first logarithm amplifier and the second logarithmically amplified signal obtained by logarithmically amplifying the input signal suitably attenuated by the attenuator by the second logarithm amplifier. A first logarithmically amplified signal and a second logarithm obtained by combining the logarithmically amplified signal and the logarithmically amplified signal with each other through resistors, or by logarithmically amplifying the input signal suitably amplified by the amplifier by the first logarithm amplifier. It has been proposed to output a logarithmically amplified signal by combining a second logarithmically amplified signal obtained by logarithmically amplifying an input signal with an amplifier through resistors.

0004

[Problems to be solved] However, in the conventional logarithmic amplifier, the first and second logarithmically amplified signals are combined via a resistor, so (i) the saturation point of the first logarithmically amplified signal and the saturation point of the first logarithmically amplified signal There is a drawback that the rising points of the two logarithmically amplified signals are combined with each other, resulting in (ii) distortion occurring at the combining point of the first and second logarithmically amplified signals.

Therefore, in order to eliminate these drawbacks, the present invention combines a first logarithmically amplified signal obtained by logarithmically amplifying an input signal applied to an input terminal in a first logarithmically amplifying circuit and a second logarithmically amplified signal. The input signal applied to the input terminal is suitably attenuated by the logarithmic amplifier circuit, and then the second logarithmically amplified signal obtained by logarithmically amplifying the signal is combined in a linear region, or the first logarithmically amplifying circuit A first logarithmically amplified signal obtained by appropriately amplifying the input signal applied to the input terminal and then logarithmically amplifying the signal, and a logarithmically amplifying signal obtained by logarithmically amplifying the input signal applied to the input terminal in a second logarithmically amplifying circuit. It is an object of the present invention to provide a logarithmic amplification device in which the dynamic range is expanded by combining the obtained second logarithmically amplified signals in a linear region.

[0006]

[Structure of the invention]

[0007]

[Means for solving the problem] The means for solving the problem provided by the present invention is as follows.
The first logarithmically amplified signal obtained by logarithmically amplifying the logarithmically amplified signal and the input signal applied to the input terminal are attenuated by an attenuator, and the second logarithmically amplified signal obtained by logarithmically amplifying the second logarithmically amplified signal.
or a first logarithmically amplified signal obtained by amplifying the input signal applied to the input terminal with an amplifier and then logarithmically amplifying it with a first logarithm amplifier. A logarithmic amplifier device that logarithmically amplifies an input signal and outputs the resultant signal from an output terminal by combining a given input signal with a second logarithmically amplified signal obtained by logarithmically amplifying the input signal with a second logarithm amplifier. (a) first and second fixed contacts are respectively connected to the output terminal of the first logarithmic amplifier and the output terminal of the first setter, and the movable contact is connected to the output terminal; Outputs the first logarithmically amplified signal VO1 when the first logarithmically amplified signal VO1 given from the output end of the first logarithmic amplifier is less than or equal to the first setting signal VR1 given from the output end of the first setter. When the first logarithmically amplified signal VO1 passed toward the terminal and given from the output end of the first logarithmic amplifier exceeds the first setting signal VR1 given from the output end of the first setting device. (b) a changeover switch (23) for passing the first setting signal VR1 toward the output terminal; and (b) a first, The second input terminals are connected to each other, and the output terminal is connected to the control terminal of the changeover switch (23), so that the first logarithmically amplified signal VO1 given from the output terminal of the first logarithmic amplifier is When the setting signal VR1 is exceeded, the selector switch (2
A control signal is generated to switch the movable contact of 3) from the first fixed contact to the second fixed contact, and the changeover switch (23
), a first comparator (24) for feeding the control end of (
c) The first and second input terminals are respectively connected to the output terminal of the second logarithmic amplifier and the output terminal of the second setter, and the The second logarithmically amplified signal VO2 and the first logarithmically amplified signal VO1 given from the output end of the second setter are the first setting signal VR1.
According to the value of the input signal VI when a second comparator (34) for output; and (d)
It is arranged between the output end of the second comparator (34) and the output terminal, and outputs the difference signal VO2-VR2 output from the output end of the second comparator (34) only when it is positive. and a diode (35) for allowing the signal to pass toward the terminal.

[0008]

[Operation] Since the logarithmic amplifier according to the present invention has the configuration specified in the column of [Means for solving problems] above,
(i) acts to combine the first and second logarithmically amplified signals with each other in a linear region, and (ii) acts to remove distortion from the combination point of the first and second logarithmically amplified signals, resulting in (iii) acts to expand the dynamic range.

[0009]

[Embodiments] Next, preferred embodiments of the logarithmic amplifier according to the present invention will be described, and with reference to the attached drawings,
I will explain in detail.

However, in the embodiments described below,
The description is provided to facilitate or accelerate the understanding of the present invention, and is not described to limit the present invention.

In other words, each element disclosed in the embodiments described below includes all design changes and equivalent substitutions that fall within the spirit and technical scope of the present invention.

(Attached drawing)

FIG. 1 is a block diagram showing an embodiment of a logarithmic amplifier according to the present invention.

FIG. 2 is a characteristic diagram for explaining the operation of the embodiment shown in FIG. Logarithmically amplified signals VO1 and VO2 are shown.

FIG. 3 is a characteristic diagram for explaining the operation of the embodiment shown in FIG. A logarithmically amplified signal VO obtained by combining the logarithmically amplified signals VO1 and VO2 is shown.

(Configuration of Example)

First, the configuration of an embodiment of the logarithmic amplifier according to the present invention will be explained in detail with reference to FIG.

10 is a logarithmic amplifier according to the present invention, which is disposed between an input terminal 11 and an output terminal 12, logarithmically amplifies the input signal VI applied to the input terminal 11 and outputs a signal (“ Logarithmic amplifier circuit 20 for generating VO1 (referred to as "logarithmically amplified signal") and outputting it from output terminal 12
is arranged in parallel with the logarithmic amplifier circuit 20, and after appropriately attenuating the input signal VI applied to the input terminal 11, logarithmically amplifies it and outputs another signal (“logarithmically amplified signal”).
A logarithmic amplification circuit 30 is provided for generating VO2 (referred to as VO2) and combining it with a logarithmically amplified signal VO1 in its linear region and outputting the resultant signal from an output terminal 12.

The logarithmic amplifier circuit 20 includes a logarithmic amplifier 21 for logarithmically amplifying the input signal VI applied to the input terminal from the input terminal 11 and outputting the logarithmically amplified signal VO1, and a logarithmic amplifier 21 for outputting the logarithmically amplified signal VO1. 1 fixed contact 23a
is connected, and the second fixed contact 23b is connected to the movable piece (i.e., the output end) of the setting device 22, and the logarithmically amplified signal V given from the output end of the logarithmic amplifier 21 is connected.
When O1 is less than or equal to the setting signal VR1 given from the setting device 22, the logarithmically amplified signal VO1 is passed toward the output terminal 12, and the logarithmically amplified signal VO1 given from the output terminal of the logarithmic amplifier 21 is given from the setting device 22. set signal V
When it is larger than R1, the setting signal VR1 is output to the terminal 12.
First and second input terminals are respectively connected to a changeover switch 23 for allowing the signal to pass through, the output terminal of the logarithmic amplifier 21, and the movable piece (i.e., the output terminal) of the setting device 22, and the output terminal is The logarithmically amplified signal VO1, which is connected to the control end of the changeover switch 23 and given from the output end of the logarithmic amplifier 21, is the setting signal VR given from the setting device 22.
a comparator 24 for generating a control signal for instructing to switch the movable contact 23c of the changeover switch 23 from the fixed contact 23a to the fixed contact 23b when the value becomes larger than 1 and applying it to the control end of the changeover switch 23; It includes a resistor 25 inserted between the movable contact 23c of the switch 23 and the output terminal 12. By the way, setting device 2
The setting signal VR1 of No. 3 is a value in the linear region of the logarithmically amplified signal VO1 given from the logarithmic amplifier 21, and is particularly preferably a value near its saturation point.

The logarithmic amplifier circuit 30 has an input end connected to the input terminal 11, and receives the input signal VI given from the input terminal 11 by a predetermined amount ATT (that is, the linear region of the logarithmically amplified signal VO1 and the linear region of the logarithmically amplified signal VO2). an attenuator 31 for attenuating the linear region (as appropriate so that the same input signal VI exists at the same time); Signal (i.e. attenuated input signal) VIA
a logarithmic amplifier 32 for logarithmically amplifying the signal and outputting it as a logarithmically amplified signal VO2; ) for outputting a difference signal VO2-VR2 between the logarithmically amplified signal VO2 given from the output end of the logarithmic amplifier 32 and the setting signal VR2 given from the output end of the setting device 33. 34
and the input terminal is connected to the output terminal of the comparator 34, and only when the difference signal VO2-VR2 output from the comparator 34 is positive (that is, when the logarithmically amplified signal VO2 exceeds the setting signal VR2) Diode 3 for passing
5, and a resistor 36 inserted between the output end of the diode 35 and the output terminal 12. Incidentally, the setting signal VR2 of the setting device 33 is a value in the linear region of the logarithmically amplified signal VO2 given from the logarithm amplifier 32,
In particular, a value near the rising point is preferable. Setting device 23
The setting signal VR1 of the setting device 33 and the setting signal VR2 of the setting device 33 are as follows.
Logarithmically amplified signal VO1 at the same value of input signal VI
, is the value of VO2.

(Effect of the embodiment)

Further, the operation of an embodiment of the logarithmic amplifier according to the present invention will be explained in detail with reference to FIGS. 1 to 3.

[0023] Overall operation

The logarithmic amplifier 10 according to the present invention receives an input signal VI applied to the input terminal 11 in the logarithmic amplifier circuit 20.
is logarithmically amplified to generate a logarithmically amplified signal VO1, which is outputted from the output terminal 12 as described later, and is also applied to the input terminal 11 by the logarithmically amplifying circuit 30 arranged in parallel to the logarithmically amplifying circuit 20. After appropriately attenuating the input signal VI, the input signal VI is logarithmically amplified to generate another logarithmically amplified signal VO2, which is output from the output terminal 12 as described later. Thereby, the logarithmic amplifier 10 according to the present invention has the input terminal 1
A logarithmically amplified signal VO1 and a logarithmically amplified signal VO2 generated from an input signal VI given to the output terminal 1 are combined in a linear region and output from an output terminal 12 as a logarithmically amplified signal VO.

Operation of logarithmic amplifier circuit 20

In the logarithmic amplifier circuit 20, first, the logarithmic amplifier 21 logarithmically amplifies the input signal VI applied to the input terminal from the input terminal 11, and outputs it to the fixed contact 23a of the changeover switch 23 as a logarithmically amplified signal VO1. ing.

The changeover switch 23 operates in response to a control signal from a comparator 24 connected to the control end, and (i
) When the logarithmically amplified signal VO1 given from the output terminal of the logarithmic amplifier 21 is less than the setting signal VR1 given from the setter 22, the logarithmically amplified signal VO1 is passed through the resistor 25 toward the output terminal 12, and ( ii) Logarithmic amplifier 2
When the logarithmically amplified signal VO1 given from the output terminal of 1 is larger than the setting signal VR1 given from the setting device 22,
The setting signal VR1 is passed through the resistor 25 toward the output terminal 12. Incidentally, the signal VA applied from the changeover switch 23 to the resistor 25 is as shown in FIG.

The comparator 24 changes the movable contact 23c of the changeover switch 23 to a fixed contact when the logarithmically amplified signal VO1 applied from the output terminal of the logarithmic amplifier 21 becomes larger than the setting signal VR1 applied from the setting device 22. A control signal instructing switching from the fixed contact 23a to the fixed contact 23b is generated and output toward the control end of the changeover switch 23.

Operation of logarithmic amplifier circuit 30

In the logarithmic amplifier circuit 30, first, the attenuator 31
However, the input signal VI applied from the input terminal 11 is attenuated by a predetermined amount ATT to form an attenuated input signal VIA.

The logarithmic amplifier 32 logarithmically amplifies the attenuated input signal VIA and outputs it as a logarithmically amplified signal VO2.

The comparator 34 receives a difference signal VO2- between the logarithmically amplified signal VO2 applied from the output end of the logarithmic amplifier 32 and the setting signal VR2 applied from the output end of the setter 33.
Creating and outputting VR2.

Difference signal VO2-VR output from comparator 34
2 passes through the diode 35 and is applied to the output terminal 12 via the resistor 36 only when it is positive (that is, when the logarithmically amplified signal VO2 exceeds the setting signal VR2). Incidentally, the signal VB applied from the diode 35 to the resistor 36 is as shown in FIG.

(Modification) In the above description, the case where the input signal is attenuated before being logarithmically amplified in the logarithmic amplifier circuit 30 has been described, but the present invention is not limited to this, and the logarithmic amplifier circuit 30 The present invention also includes a case where the input signal is amplified in the logarithmic amplifier circuit 20 before being logarithmically amplified instead of attenuating the input signal in the logarithmically amplifying circuit 20 .

[0035]

[Effects of the Invention] As is clear from the above, the logarithmic amplification device according to the present invention has the configuration specified in the column of [Means for solving problems]. (i) First and second logarithms It has the effect of being able to combine the amplified signals with each other in a linear region, which in turn has the effect of (ii) being able to remove distortion from the combining point of the first and second logarithmically amplified signals, and as a result (iii) expanding the dynamic range. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a logarithmic amplifier according to the present invention.

FIG. 2 is a characteristic diagram for explaining the operation of the embodiment shown in FIG. 1;

FIG. 3 is a characteristic diagram for explaining the operation of the embodiment shown in FIG. 1;

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: A first logarithmically amplified signal obtained by logarithmically amplifying an input signal applied to an input terminal with a first logarithmic amplifier and an input signal applied to the input terminal, and then attenuating the input signal applied to the input terminal with an attenuator. The second logarithmically amplified signal obtained by logarithmically amplifying the second logarithmically amplifier is combined with each other, or the input signal given to the input terminal is amplified by the amplifier and then logarithmically amplified by the first logarithmically amplifier. By combining together the first logarithmically amplified signal obtained by the first logarithmically amplified signal and the second logarithmically amplified signal obtained by logarithmically amplifying the input signal given to the input terminal by the second logarithm amplifier, the input signal is (a) first and second fixed contacts are connected to the output terminal of the first logarithmic amplifier and the output terminal of the first setter, respectively; and a movable contact is connected to the output terminal, and the first logarithmically amplified signal VO1 given from the output terminal of the first logarithmic amplifier is set to a first setting given from the output terminal of the first setting device. When the signal VR1 is below, the first logarithmically amplified signal VO1 is passed toward the output terminal, and the first logarithmically amplified signal VO1 given from the output terminal of the first logarithm amplifier is the output of the first setter. When the first setting signal VR1 given from the end is exceeded, the first
(b) a changeover switch (23) for passing the setting signal VR1 toward the output terminal; The input ends are each connected and the output end is a selector switch (
23), and the first logarithmically amplified signal VO1 given from the output terminal of the first logarithm amplifier is connected to the control terminal of the first logarithm amplifier.
When the setting signal VR1 is exceeded, the selector switch (23)
a first comparator (24) for generating a control signal to switch the movable contact from the first fixed contact to the second fixed contact and applying it to the control end of the changeover switch (23);
The first and second input terminals are respectively connected to the output terminal of the second logarithmic amplifier and the output terminal of the second setter,
When the second logarithmically amplified signal VO2 given from the output terminal of the second logarithmic amplifier and the first logarithmically amplified signal VO1 given from the output terminal of the second setter become the first setting signal VR1, A second setting signal VR that takes the same value as the second logarithmically amplified signal VO2 depending on the value of the input signal VI.
(d) a second comparator (34) for generating a difference signal VO2-VR2 between the two and outputting it from the output terminal;
The difference signal VO2-VR2 output from the output terminal of the second comparator (34) is connected to the output terminal only when it is positive. A logarithmic amplifier characterized by comprising a diode (35) for directing and passing the signal.