JP2769929B2 - Logarithmic amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a logarithmic amplifier,
In particular, a first logarithmic amplified signal obtained by logarithmically amplifying an input signal given to an input terminal by a first logarithmic amplifier and a second logarithmic amplified signal
The input signal given to the input terminal is appropriately attenuated by the logarithmic amplifier circuit of (1), and the second logarithmic amplified signal obtained by logarithmic amplification is combined in series in the respective linear regions, or A logarithmic amplifier circuit appropriately amplifies an input signal supplied to an input terminal, and then logarithmically amplifies the first logarithmic amplified signal and the second logarithmic amplifier circuit, which logarithmizes the input signal supplied to the input terminal. The present invention relates to a logarithmic amplifier having a dynamic range extended by combining in series respective linear regions with amplified second logarithmic amplified signals.

[0003]

2. Description of the Related Art Conventionally, as a logarithmic amplifier of this kind,
A first logarithmic amplified signal obtained by logarithmic amplification of the input signal by the first logarithmic amplifier and a second logarithmic amplifier obtained by logarithmically amplifying the input signal appropriately attenuated by the attenuator by a second logarithmic amplifier. A first logarithmic amplified signal and a second logarithmic signal obtained by combining logarithmic amplified signals with each other via a resistor or by logarithmically amplifying an input signal appropriately amplified by an amplifier by a first logarithmic amplifier. A second logarithmic amplified signal obtained by logarithmically amplifying the input signal by the amplifier is combined with each other via a resistor, thereby achieving dynamics.
Something that extends the cleanse was proposed.

[0004]

A problem to be, however, in the conventional logarithmic amplification device, via the first resistor, a second logarithmic amplifier signal thereof
Since still have synthesized, there is disadvantage that synthesized in parallel with each other and falling over point (i) and the saturation point of the first logarithmic amplifying signals second logarithmic amplifying signals, consequently (ii) second There is a disadvantage that distortion occurs at the synthesis point of the first and second logarithmically amplified signals.

Therefore, the present invention aims to eliminate these drawbacks and to provide a first logarithmic amplifier and a second logarithmic amplified signal obtained by logarithmically amplifying an input signal supplied to an input terminal by a first logarithmic amplifier. The input signal given to the input terminal is appropriately attenuated by the logarithmic amplifier circuit of (1), and the second logarithmic amplified signal obtained by logarithmic amplification is combined in series in the respective linear regions, or A logarithmic amplifier circuit appropriately amplifies an input signal supplied to an input terminal, and then logarithmically amplifies the first logarithmic amplified signal and the second logarithmic amplifier circuit, which logarithmizes the input signal supplied to the input terminal. It is an object of the present invention to provide a logarithmic amplifier having an extended dynamic range by combining the amplified second logarithmic amplified signal and the respective linear regions in series .

[0006]

Configuration of the Invention

[0007]

A solution to the problem provided by the present invention is that "an input signal supplied to an input terminal is changed to a first signal.
The first logarithmic amplified signal obtained by logarithmic amplification by the logarithmic amplifier and the input signal given to the input terminal are attenuated by the attenuator, and the second logarithmic amplifier obtained by logarithmic amplification by the second logarithmic amplifier.
Or the first logarithmic amplified signal obtained by amplifying the input signal given to the input terminal with an amplifier and then logarithmically amplifying the signal with the first logarithmic amplifier and the input terminal. A logarithmic amplifier configured to logarithmically amplify an input signal and output from an output terminal by combining the input signal with a second logarithmically amplified signal obtained by logarithmically amplifying the input signal with a second logarithmic amplifier. Wherein (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 setting device, and the movable contact is connected to the output terminal; The first logarithmic amplified signal V _{O1 supplied} from the output terminal of the first logarithmic amplifier is applied to the first setting signal V _{R1 supplied} from the output terminal of the first setting device.
In the following case, the first logarithmic amplified signal V _O1 is passed toward the output terminal, and the first logarithmic amplified signal V _O1 given from the output terminal of the first logarithmic amplifier is output from the first setting unit. When the first set signal V _R1 given from the end is exceeded, the first
A changeover switch (23) for passing the setting signal V _R1 toward the output terminal; and (b) a first and a second output terminal of the first logarithmic amplifier and the output terminal of the first setting device. Are connected to the control terminal of a change-over switch (23), respectively, and the first logarithmic amplified signal V _{O1 supplied} from the output terminal of the first logarithmic amplifier is set to a first setting. When the signal V _R1 is exceeded, a control signal is generated to switch the movable contact of the changeover switch (23) from the first fixed contact to the second fixed contact, and the changeover switch (2
(C) a first comparator (24) for application to a control terminal of (3), and (c) a first and second input terminals for an output terminal of the second logarithmic amplifier and an output terminal of the second setting device. Are connected to each other, and a second logarithmic amplified signal V _{O2 supplied} from the output terminal of the second logarithmic amplifier and a first logarithmic amplified signal V _{O1 supplied} from the output terminal of the second setting unit are connected to the second logarithmic amplifier. second logarithmic amplification signal V in accordance with the value of the input signal V _I when the first setting signal V _R1
A second comparator (34) for generating a difference signal V _O2 −V _R2 between the second setting signal V _R2 having the same value as that of _O2 and outputting the difference signal from the output end; d) The difference signal V _O2 −V _R2 output from the output terminal of the second comparator (34), which is disposed between the output terminal of the second comparator (34) and the output terminal, has a positive value. A diode (35) for passing the signal toward the output terminal only when the first logarithm
The amplified signal and the second logarithmic amplified signal are respectively divided into linear regions.
And a logarithmic amplifying device characterized in that they are combined in series .

[0008]

The logarithmic amplifier according to the present invention has the configuration specified in the above-mentioned "Means for Solving the Problems". Therefore, (i) the first and second logarithmic amplification signals are converted into respective linear regions. Performs an operation of combining in series with each other, and (ii) an operation of removing distortion from a synthesis point of the first and second logarithmic amplified signals, and (iii) an operation of extending the dynamic range.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a logarithmic amplifier according to the present invention.

However, the embodiments described below are:
It is described for the purpose of facilitating or facilitating the understanding of the present invention and is not described for limiting the present invention.

In other words, each element disclosed in the embodiments described below includes all design changes and equivalent replacements that fall within the spirit and 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.

[0014] Figure 2 is a characteristic diagram for explaining the operation of the embodiment shown in FIG. 1, in particular, is logarithmically amplified by the input signal V _I and the logarithmic amplifier 21, 32 is applied to the input terminal 11 The logarithmically amplified signals V _O1 and V _O2 are shown.

[0015] Figure 3 is a characteristic diagram for explaining the operation of the embodiment shown in FIG. 1, in particular, the input signal V _I applied to input terminal 11, it is logarithmically amplified by a logarithmic amplifier 21
The signal _{VA obtained} by switching the logarithmic amplification signal V _O1 and the logarithmic amplification
Switching of logarithmically amplified signal V _O2 logarithmically amplified by device 32
And a signal V _B synthesized in parallel with each other, resulting in logarithmic amplification
Shows a logarithmic amplification signal V _O which is obtained form if <br/> series with each other in each of the linear region of the signal V _O1, V _O2.

(Configuration of Embodiment)

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

[0018] 10 is a logarithmic amplifier according to the present invention, the input terminals 11 and arranged to have an input signal V _I is applied to the input terminal 11 logarithmically amplifies the signal between the output terminal 12
A logarithmic amplifier circuit 20 for generating V _O1 and outputting it from an output terminal 12, and an input signal provided in parallel with the logarithmic amplifier circuit 20 and given to an input terminal 11 After appropriately attenuating V _I , it is logarithmically amplified to generate another signal (referred to as “logarithmically amplified signal”) V _O2 , combined in series with logarithmic amplified signal V _O1 in a linear region thereof, and output from output terminal 12. And a logarithmic amplifier circuit 30 . here
Combining in series means the characteristics of each logarithmically amplified signal
Are connected linearly with continuity.

The logarithmic amplifier circuit 20 logarithmically amplifies the input signal VI _supplied from the input terminal 11 to the input terminal, and performs logarithmic amplification of the signal V _I.
Logarithmic amplifier 21 for outputting as _O1 , and logarithmic amplifier 21
The first fixed contact 23a is connected to the output end of the setter 22, and the second fixed contact 23b is connected to the movable piece (that is, the output end) of the setter 22, and is supplied from the output end of the logarithmic amplifier 21. When the logarithmic amplified signal V _O1 is equal to or less than the setting signal V _R1 given from the setting unit 22, the logarithmic amplified signal V _O1 is output to the output terminal.
When the logarithmic amplification signal V _{O1 supplied} from the output terminal of the logarithmic amplifier 21 is larger than the setting signal V _{R1 supplied} from the setting unit 22, the setting signal V _R1 is output to the output terminal.
A first switch and a second switch are connected to an output terminal of the logarithmic amplifier 21 and a movable piece (that is, an output terminal) of the setter 22, respectively, and the output terminal is connected to the output terminal. Is connected to the control terminal of the changeover switch 23, and the logarithmically amplified signal V _O1 given from the output terminal of the logarithmic amplifier 21
Is larger than the setting signal _VR1 given from the setting device 22, the movable contact 23c of the changeover switch 23 is changed to the fixed contact 23.
a from a to a fixed contact 23b, a comparator 24 for generating a control signal for giving a command to the control terminal of the changeover switch 23, and a resistor inserted between the movable contact 23c of the changeover switch 23 and the output terminal 12. 25 and. Incidentally, the setting signal V _R1 of the setting unit 23 is a value in the linear region of the logarithmic amplified signal V _O1 given from the logarithmic amplifier 21, and is particularly preferably a value near the saturation point.

The logarithmic amplifier circuit 30 has an input terminal connected to the input terminal 11 and an input signal V _I supplied from the input terminal 11.
By a predetermined amount A _TT (that is, the input signal V in which the linear region of the logarithmic amplified signal V _{O1 and} the linear region of the log amplified signal V _O2 are the same)
An attenuator 31 for appropriate) allowed to attenuate to exist simultaneously for _I, the input signal (i.e. attenuation input signal attenuated by the attenuator 31 whose input terminal is connected to an output terminal of the attenuator 31) V A logarithmic amplifier 32 for logarithmically amplifying _IA and outputting it as a logarithmically amplified signal V _O2 , one input terminal being connected to the output terminal of logarithmic amplifier 32 and the other input terminal being a movable piece of setter 33 (that is, Output terminal) and a logarithmic amplified signal V _O2 given from the output terminal of the logarithmic amplifier 32.
And a comparator 34 for outputting a difference signal V _O2 −V _R2 between the output signal of the setting device 33 and the setting signal V _R2 provided from the output terminal of the setting device 33, and an input terminal thereof is connected to the output terminal of the comparator 34. And comparator 34
, And a diode 35 for allowing the signal to pass only when the difference signal V _O2 −V _R2 is positive (that is, when the logarithmic amplification signal V _O2 exceeds the set signal V _R2 ), the output terminal of the diode 35 and the output terminal 12 And a resistor 36 inserted between them. Incidentally, the setting signal V _R2 of the setting unit 33 is a logarithmic amplifier.
A value in the linear region of the logarithmic amplified signal V _O2 given from 32, particularly a value near the rising point thereof, is preferable. Setting signal V _R2 of the setting signal V _R1 and setter 33 of setter 23
The logarithmic amplification signal V of the same value of the input signal V _I
These are the values of _O1 and V _O2 . In addition, the dynamic range has decreased.
It is divided expanded in accordance with the attenuation A _TT of衰器31.

(Operation of Embodiment)

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

The whole dynamic |

The logarithmic amplifier according to the present invention 10, the input signal V _I is applied to the input terminal 11 in a logarithmic amplifier 20 logarithmically amplifies generate logarithmic amplification signal V _O1 output from the output terminal 12 as described below to which, together appropriately logarithmically amplified After allowed decay to another logarithmic amplification of the input signal V _I is applied to the input terminal 11 in a logarithmic amplifier 30 which is disposed in parallel to the logarithmic amplification circuit 20 Generates a signal V _O2 and outputs it as described below.
Output from 12. Thus, the logarithmic amplifier 10 according to the present invention, the logarithmic amplification signal V _O1 is generated from the input signal V _I is applied to the input terminal 11 and the logarithmic amplifier signal V _O2
The signals are combined in series in the respective linear regions and output from the output terminal 12 as a logarithmic amplified signal V _O.

Operation of Logarithmic Amplifier 20

In the logarithmic amplifier 20 , first, the logarithmic amplifier 21
However, the logarithmic amplification of the input signal VI _supplied from the input terminal 11 to the input terminal is performed and output as a logarithmic amplification signal _{V01 to} the fixed contact 23a of the changeover switch 23.

The changeover switch 23 operates in response to a control signal from a comparator 24 connected to a control terminal. (I) A logarithmic amplification signal V _{O1 supplied} from an output terminal of the logarithmic amplifier 21 is _supplied to a setting unit. When the setting signal V _R1 given from 22 or less, the resistance 25
Passed through toward the output terminal 12 of the logarithmic amplification signal V _O1 through, and (ii) than the set signal V _R1 to logarithmic amplification signal V _O1 is given from setter 22 provided from the output of logarithmic amplifier 21 When it is larger, the setting signal _VR1 is output via the resistor 25
Passing towards 12. By the way, changeover switch
The signal _VA given from 23 to the resistor 25 is as shown in FIG.

When the logarithmic amplified signal V _O1 given from the output terminal of the logarithmic amplifier 21 becomes larger than the setting signal V _R1 given from the setting unit 22, the comparator 24 changes the movable contact 23c of the changeover switch 23. A control signal for instructing switching from the fixed contact 23a to the fixed contact 23b is generated and output to the control terminal of the changeover switch 23.

Operation of logarithmic amplifier circuit 30

In the logarithmic amplifier circuit 30 , first, the attenuator 31
The input signal V _I applied from the input terminal 11 allowed attenuation by a predetermined amount A _TT, is set to attenuate the input signal V _IA.

The logarithmic amplifier 32 logarithmically amplifies the attenuated input signal V _IA and outputs it as a logarithmic amplified signal V _O2 .

The comparator 34 outputs a difference signal V _O2 −V _R2 between the logarithmic amplified signal V _O2 supplied from the output terminal of the logarithmic amplifier 32 and the setting signal V _{R2 supplied} from the output terminal of the setting unit 33. Created and output.

The difference signal V _O2 −V _R2 output from the comparator 34 is
Only when the signal is positive (that is, when the logarithmic amplified signal V _O2 exceeds the set signal V _R2 ), it passes through the diode 35 and is supplied to the output terminal 12 via the resistor 36. Incidentally, the signal V _B which is supplied from the diode 35 to the resistor 36 is as shown in FIG. That is, the logarithmic amplifier of the present invention
The characteristic of the logarithm is that the logarithm
The signal _{VA obtained} by switching the amplified signal V _O1 and the logarithmic amplifier 32
Therefore, the logarithmically amplified logarithmically amplified signal V _O2 switched signal
Synthesized in parallel via each other resistor and V _B, resulting in pairs
In the linear regions of the amplified signals V _O1 and V _O2 ,
Is to combine them into columns.

It should be noted (Modification) In the above description, the input signal at the logarithmic amplifying circuit 30 has been described for the case to be attenuated prior to logarithmic amplification, the present invention is not limited thereto, logarithmic amplification circuit 30 Instead of attenuating the input signal prior to logarithmic amplification, the logarithmic amplifier 20 also includes a case where the input signal is amplified prior to logarithmic amplification.

[0035]

As apparent from the above description, the logarithmic amplifier according to the present invention has the configuration specified in the column of [Means for Solving the Problems]. (I) First and second logarithms It has the effect that the amplified signals can be combined in series with each other in the respective linear regions, and (ii) has the effect of removing distortion from the combined point of the first and second logarithmic amplified signals, and consequently (iii) This has the effect of expanding the dynamic range.

[Brief description of the drawings]

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] 10 ······························ Input terminal 12 Output terminal 20 Logarithmic amplifier 21 Logarithmic amplifier 22 Setting device 23・ ・ ・ ・ ・ ・ Changeover switches 23a, 23b ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Fixed contact 23c ・ ・ ・ ・ ・ ・ Movable contact 24 ・ ・ ・ ・ ・ ・ ・ ・ ・... Comparator 25 ... Resistance 30 ...・ Logarithmic amplifier 31 ・ ・ ・ ・ ・ ・ ・ ・ Attenuator 32 ・ ・ ・ ・ ・ ・ ・ ・ ・ Logarithmic amplifier 33 ・ ・・ ・ ・ ・ ・ ・ ・ ・ Setting device 34 ・ ・ ・ ・ ・ ・ ・ ・ Comparator 35 ・ ・ ・..................... Diode 36 ........................ Resistance

Claims (1)

(57) [Claims] An attenuator attenuates a first logarithmic amplified signal obtained by logarithmically amplifying an input signal supplied to an input terminal with a first logarithmic amplifier and an input signal supplied to the input terminal. A second logarithmic amplifier and a second logarithmic amplified signal obtained by logarithmic amplification are combined with each other, or an input signal supplied to an input terminal is amplified by an amplifier and then logarithmically amplified by a first logarithmic amplifier. The first logarithmic amplified signal obtained as a result and the second logarithmic amplified signal obtained by logarithmically amplifying the input signal supplied to the input terminal with a second logarithmic amplifier are combined with each other to obtain an input signal. A logarithmic amplifier for logarithmically amplifying and outputting from an output terminal: (a) first and second fixed contacts respectively correspond to an output terminal of a first logarithmic amplifier and an output terminal of a first setting device; Connected and the movable contact is connected to the output terminal Ri, the first setting signal V _R1 of the first logarithmic amplifier signal V _O1 provided from the output of the first logarithmic amplifier is given from the output end of the first setter
In the following case, the first logarithmic amplified signal V _O1 is passed toward the output terminal, and the first logarithmic amplified signal V _O1 given from the output terminal of the first logarithmic amplifier is output from the first setting unit. When the first set signal V _R1 given from the end is exceeded, the first
A changeover switch (23) for passing the setting signal V _R1 toward the output terminal; and (b) a first and a second output terminal of the first logarithmic amplifier and the output terminal of the first setting device. Are connected to the control terminal of a change-over switch (23), respectively, and the first logarithmic amplified signal V _{O1 supplied} from the output terminal of the first logarithmic amplifier is set to a first setting. When the signal V _R1 is exceeded, a control signal is generated to switch the movable contact of the changeover switch (23) from the first fixed contact to the second fixed contact, and the changeover switch (2
(C) a first comparator (24) for application to a control terminal of (3), and (c) a first and second input terminals for an output terminal of the second logarithmic amplifier and an output terminal of the second setting device. Are connected to each other, and a second logarithmic amplified signal V _{O2 supplied} from the output terminal of the second logarithmic amplifier and a first logarithmic amplified signal V _{O1 supplied} from the output terminal of the second setting unit are connected to the second logarithmic amplifier. second logarithmic amplification signal V in accordance with the value of the input signal V _I when the first setting signal V _R1
A second comparator (34) for generating a difference signal V _O2 −V _R2 between the second setting signal V _R2 having the same value as that of _O2 and outputting the difference signal from the output end; d) The difference signal V _O2 −V _R2 output from the output terminal of the second comparator (34), which is disposed between the output terminal of the second comparator (34) and the output terminal, has a positive value. A diode (35) for passing the signal toward the output terminal only when the first logarithm
The amplified signal and the second logarithmic amplified signal are respectively divided into linear regions.
A logarithmic amplifier characterized in that the signals are combined in series .