JPH04282910A - Logarithmic amplifier - Google Patents

Abstract

PURPOSE:To expand the dynamic range by synthesizing at a linear region a 1st logarithmic amplifier signal obtained by logarithmically amplifying an input signal at a 1st amplifier circuit and a 2nd logarithmic amplifier signal obtained by attenuating and logarithmically amplifying the input signal at a 2nd amplifier circuit. CONSTITUTION:A logarithmic amplifier 21 of a logarithmic amplifier circuit 20 applies logarithmic amplification to an input signal V1 and a resulting signal VO1 is outputted to a changeover switch 23 and a sample-and-hold circuit 22. The signal VO1 is outputted to an output terminal 12 through the switch 23 whose moving contact 23c is thrown when a control signal S1 is given from a comparator 37. On the other hand, an attenuator 31 of a logarithmic amplifier circuit 30 attenuates the input signal V1 by processing quantity, logarithmic amplification is implemented by a logarithmic amplifier 32 and a signal VO2 is outputted. Only when the signal VO2 is larger than a setting signal 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 circuit 20, 30 are synthesized at a linear region and the result is outputted. 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 were simply combined via a resistor, so (i) saturation of the first logarithmically amplified signal There is a drawback that the rising point of the second logarithmically amplified signal and the rising point of the second logarithmically amplified signal are combined with each other, and as a result, (ii) the first and second
The disadvantage is that distortion occurs at the point where the logarithmically amplified signals are combined.

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) The input terminal is connected to the output terminal of the first logarithmic amplifier, and when the first control signal is given to the control terminal, the input terminal is connected to the output terminal of the first logarithmic amplifier. (b) a sample hold circuit (22) for holding the first logarithmically amplified signal VO1 and outputting it from the output terminal as a holding value VR1;
The output terminal of the first logarithmic amplifier and the sample and hold circuit (
The first and second fixed contacts are respectively connected to the output terminal of 22), and the movable contact is connected to the output terminal,
By switching the movable contact between the first and second fixed contacts in response to the second control signal given to the control end becoming positive, sample and hold is performed when the second control signal is given. (c) a changeover switch (23) for passing the held value VR1 given from the output end of the circuit (22) toward the output terminal; and (c) an output end of the second logarithmic amplifier and an output end of the setting device. On the other hand, the first and second input terminals are respectively connected, and the second logarithmically amplified signal VO2 given from the output terminal of the second logarithmic amplifier and the setting signal VR2 given from the output terminal of the setting device are connected to each other. The difference signal between VO2-VR2
The first comparator (3
4) and (d) a difference signal VO2-VR2 arranged between the output terminal and the output terminal of the first comparator (34) and output from the output terminal of the first comparator (34). (e) a diode (35) for passing the signal toward the output terminal only when it is positive; and the output end is connected to the control end of the changeover switch (23), and the second logarithm amplified signal VO2 given from the output end of the second logarithmic amplifier and the second logarithm amplified signal VO2 given from the output end of the setting device a second comparator for comparing the setting signal VR2 with the first logarithmically amplified signal VO2 and providing the comparison result as a second control signal to the control end of the changeover switch (23) when the first logarithmically amplified signal VO2 is larger than the setting signal VR2; (37) and (f) second
The input end is connected to the output end of the comparator (37), and the output end is connected to the control end of the sample and hold circuit (22), and a second control signal is applied from the second comparator (37). a one-shot pulse generation circuit (38) for generating a pulse when the signal is input and applying it to the sample-and-hold circuit (22) as a first control signal.

[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 it as a logarithmically amplified signal VO1, and an input terminal for the output terminal of the logarithmic amplifier 21. The logarithmically amplified signal V given from the output end of the logarithmic amplifier 21
A sample and hold circuit 22 is provided for holding O1 at the control end when the control signal S2 is applied and outputting the held value VR1 of the logarithmically amplified signal VO1 from the output end; The first fixed contact 23a is connected and the second fixed contact 23b is connected to the output end of the sample and hold circuit 22, and when the control signal S1 is applied to the control end, the movable contact 23c is connected to the fixed contact 23a, 23b, the logarithmically amplified signal VO given from the output terminal of the logarithm amplifier 21
1 is less than the held value VR1 of the sample and hold circuit 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 becomes the held value of the sample and hold circuit 22. VR
When it is larger than 1, the held value VR1 is output to the output terminal 12.
It is provided with a changeover switch 23 for passing through the changeover switch 23 and a resistor 24 inserted between the movable contact 23c of the changeover switch 23 and the output terminal 12. Incidentally, the held value VR1 of the sample and hold circuit 22 is a value in the linear region of the logarithmically amplified signal VO1 outputted from the logarithmic amplifier 21, and is particularly preferably a value near the 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, a resistor 36 inserted between the output terminal of the diode 35 and the output terminal 12, and one input terminal connected to the logarithmic amplifier 32.
is connected to the output terminal of the setting device 3, and the other input terminal is connected to the output terminal of the setting device 3.
The logarithmically amplified signal VO is connected to the movable piece (i.e., the output end) of the logarithm amplifier 32 and is applied from the output end of the logarithm amplifier 32.
2 and the setting signal VR2 given from the output terminal of the setting device 33
are compared with each other, and the logarithmically amplified signal VO2 becomes the setting signal VR2.
a comparator 37 for outputting the comparison result as a control signal S1 to the control end of the changeover switch 23 when the value is greater than It is connected to the control end of the circuit 22 and operates the sample and hold circuit 22 when the control signal S1 is applied (specifically, when the logarithmically amplified signal VO2 becomes larger than the setting signal VR2 and the control signal S1 rises). Sample and hold circuit 2 generates a single pulse and uses it as control signal S2.
The one-shot pulse generating circuit 38 is provided for supplying a one-shot pulse to the second control terminal. Incidentally, it is preferable that the setting signal VR2 of the setting device 33 be a value in the linear region of the logarithmically amplified signal VO2 given by the logarithmic amplifier 32, and in particular, a value near its rising point. As is clear from the mechanism of generation of the held value VR1, the held value VR1 given from the sample and hold circuit 22 and the setting signal VR2 given from the setter 33 are equivalent to the logarithmically amplified signals VO1 and VO2 at the same value of the input signal VI. It is a value.

(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 from the input terminal 11 to the input terminal, and outputs the logarithmically amplified signal VO1 to the fixed contact 23a of the changeover switch 23 and the sample hold circuit. It outputs to the input terminal of 22.

The sample and hold circuit 22 holds and holds the logarithmically amplified signal VO1 provided from the logarithmic amplifier 21 when a control signal S2 is provided to the control end from the one-shot pulse generation circuit 38 as described later. The fixed contact 2 of the changeover switch 23 uses the result as the holding value VR1.
Output towards 3b.

The changeover switch 23 switches the movable contact 23c from the fixed contact 23a to the fixed contact 2 when the control signal S1 is applied from the comparator 37 to the control end.
3b, and the logarithmically amplified signal VO1 is applied via the resistor 24.
and (ii) when the control signal S1 is not given from the comparator 37 to the control terminal, the held value VR1 of the sample hold circuit 22 is passed through the resistor 24 to the output terminal 12. I am directing them to pass. Incidentally, the signal VA applied from the changeover switch 23 to the resistor 24 is as shown in FIG.

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.

The comparator 37 compares the logarithmically amplified signal VO2 given from the output end of the logarithmic amplifier 32 with the setting signal VR2 given from the output end of the setter 33, so that the logarithmically amplified signal VO2 becomes the setting signal VR2. when it is larger than
The comparison result is given to the control end of the changeover switch 23 as a control signal S1, and the one-shot pulse generation circuit 3
It is applied to the input terminal of 8.

The one-shot pulse generation circuit 38 generates a single pulse when the control signal S1 is applied from the comparator 37 (specifically, when the control signal S1 rises), and outputs the single pulse to the sample-hold circuit 22 as the control signal S2. is given to the control end.

(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 .

[0037]

[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 In a logarithmic amplifier that logarithmically amplifies and outputs the logarithmic signal from an output terminal, (a) the input terminal is connected to the output terminal of the first logarithmic amplifier;
When the first control signal is given to the control end, the first
(b) a sample and hold circuit (22) for holding the first logarithmically amplified signal VO1 given from the output terminal of the logarithmic amplifier and outputting it from the output terminal as a holding value VR1; and (b) the output terminal of the first logarithmic amplifier. and sample hold circuit (22
), and a movable contact is connected to the output terminal, and the movable contact is movable in response to a positive second control signal given to the control terminal. By switching the contact between the first and second fixed contacts, the held value VR given from the output end of the sample hold circuit (22) when the second control signal is given.
(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 setting device; The output terminal generates a difference signal VO2-VR2 between the second logarithmically amplified signal VO2 applied from the output terminal of the second logarithmic amplifier and the setting signal VR2 applied from the output terminal of the setting device. a first comparator (34) for outputting from
and (d) is arranged between the output terminal and the output terminal of the first comparator (34), and is configured to correct the difference signal VO2-VR2 output from the output terminal of the first comparator (34). A diode (3
5) and (e) the first and second input terminals are respectively connected to the output terminal of the second logarithmic amplifier and the output terminal of the setting device, and the output terminal is connected to the control terminal of the changeover switch (23). is given from the output terminal of the second logarithmic amplifier.
The first logarithmically amplified signal VO2 is compared with the setting signal VR2 given from the output end of the setting device, and the first logarithmically amplified signal V
a second comparator (37) for providing the comparison result as a second control signal to the control end of the changeover switch (23) when O2 is larger than the setting signal VR2; and (f) a second comparator ( The input end is connected to the output end of the sample hold circuit (22), and the output end is connected to the control end of the sample and hold circuit (22), and when the second control signal is applied from the second comparator (37), a pulse is generated. A logarithmic amplifier comprising: a one-shot pulse generating circuit (38) for generating and applying a first control signal to a sample-and-hold circuit (22).