JP3427342B2 - Electronic circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit, and more particularly to an electronic circuit including an amplifier circuit and the like.

[0002]

2. Description of the Related Art An amplifier circuit as an example of a conventional electronic circuit divides an output voltage of an operational amplifier A1 by a resistor R1 and a resistor R2 and divides the voltage applied to the resistor R1 as shown in FIG. A voltage is applied to the inverting input terminal of the operational amplifier A1 to form a non-inverting amplifier circuit. Here, the resistors R1 and R2 are resistors for determining the closed gain of the amplifier circuit.

When the conventional amplifier circuit as described above is actually constructed, the resistance Z due to the resistance due to the pattern or wiring on the wiring board and the impedance due to the reactance is the resistance R1.
Exists between the earth and the earth.

[0004]

Therefore, when the input voltage is vi and the output voltage is vo, the closed gain G of the conventional amplifier circuit described above is ideal for the operational amplifier A1 having infinite input impedance and infinite gain. The operational amplifier is represented by the following equation (1).

[0005]   G = vo / vi = (R1 + R2 + Z) / (R1 + Z) (1)

However, as is clear from the equation (1), when an amplifier circuit is actually constructed, an unknown impedance Z is added, and thus an accurate closed gain (closed gain is also referred to as an amplification factor) cannot be obtained. There was a problem.

Further, since the value of the unknown impedance Z varies depending on the frequency, the closed gain of the amplifier circuit varies depending on the frequency of the input voltage vi. For this reason, when the amplifier circuit is actually configured, there arises a problem that an accurate closed gain that does not fluctuate depending on the frequency cannot be obtained. Thus, there is a problem that the signal current or the like is changed depending on the frequency when there is an impedance or the like having an unknown value in the line through which the signal current or the like flows.

It is an object of the present invention to provide an electronic circuit that suppresses fluctuations in signal current due to frequency due to impedance of an unknown value in a line when the electronic circuit is actually constructed.

[0009]

According to a first aspect of the present invention, there is provided an electronic circuit comprising: a first resistor through which a signal current flows; an inverting amplifier connected to one end of the first resistor; and an output end of the inverting amplifier. And a second resistor connected between the other end of the first resistor and the second resistor, wherein the resistance value of the second resistor is the gain of the inverting amplifier multiplied by the resistance value of the first resistor. .

According to the electronic circuit of the first aspect of the present invention, even if the resistance due to the pattern on the wiring board, the wiring, or the impedance due to the reactance exists in series with the first resistance, The potential at one end is amplified by the inverting amplifier, the voltage of the output of the inverting amplifier is applied to the other end of the first resistor through the second resistor, and the resistance value of the second resistor is equal to that of the first resistor. Since the resistance is multiplied by the gain of the inverting amplifier, the current flowing through the first resistor into the impedance and the current flowing through the second resistor into the impedance due to frequency fluctuations cancel each other out. , The signal current becomes independent of impedance and is no longer affected by frequency.

An electronic circuit according to a second aspect of the present invention comprises an amplifier for amplifying an input voltage and a voltage dividing circuit including first and second resistors for dividing an output voltage of the amplifier, and a second resistor. One end is connected to the output end of the amplifier and the common connection point of the first and second resistors is connected to the inverting input terminal of the amplifier, and the divided voltage applied to the second resistor is applied to the inverting input terminal of the amplifier. A non-inverting amplifier circuit for amplifying the voltage at the inverting input terminal of the amplifier, and a third resistor connected between the output terminal of the inverting amplifier and the non-common connection terminal of the first resistor, It is characterized in that the resistance value of the third resistor is set to the gain of the inverting amplifier multiplied by the resistance value of the first resistor.

According to the electronic circuit of the second aspect of the present invention, when the amplifier circuit is actually configured, the resistance due to the pattern on the wiring board, the wiring, etc. and the impedance due to the reactance are the non-common connection of the first resistance. Even if it exists between the terminal and the ground, the current flowing through the first resistance into the impedance and the current flowing through the third resistance into the impedance due to frequency fluctuations have a resistance value of the third resistance. Since the resistance value of the first resistor is multiplied by the gain of the inverting amplifier, they cancel each other out, and the closed gain G of the amplifier circuit becomes independent of impedance and is determined by the first and second resistance values. When the amplifier circuit is actually configured, an accurate and accurate closed gain that does not vary depending on the frequency can be obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An electronic circuit according to the present invention will be described below with reference to an embodiment. FIG. 1 is a block diagram showing the configuration of an electronic circuit according to an embodiment of the present invention, and illustrates the case of an amplifier circuit.

In the electronic circuit according to the embodiment of the present invention, the output voltage of the operational amplifier A1 is divided by the resistors R1 and R2, and the divided voltage applied to the resistor R1 is inverted input terminal of the operational amplifier A1. To form a non-inverting amplifier circuit and supply the voltage at the inverting input terminal to the inverting amplifier with gain 〃1〃 (amplifier with gain 〃-1〃) A2 as the input voltage to output the ideal inverting amplifier A2. Voltage is R1
Is applied to the terminal end of the resistor R1 via the resistor R3 having the same resistance value. Here, the inverting amplifier A2 can be regarded as an ideal inverting amplifier having an infinite input impedance and a gain of "1" (ideal amplifier having an infinite input impedance and a gain of "-1").

In the case where an amplifier circuit as an electronic circuit is actually constructed, Z is an impedance due to a resistance or a reactance existing between the resistor R1 and the ground due to a pattern on the wiring board, wiring, etc., and E Is a DC power supply, which supplies a power supply voltage to the operational amplifier A1 and the inverting amplifier A2.

The operation of the electronic circuit according to the embodiment of the present invention will be described. In the following description, the resistance R
The resistance values of 1, R2 and R3 are also indicated by R1, R2 and R3.

When the input voltage vi is applied, the potential vb at the point b, that is, the inverting input terminal and the potential vc at the output terminal c of the inverting amplifier A2 are caused by an imaginary short circuit between the non-inverting input terminal and the inverting input terminal of the operational amplifier A1. , As shown in the following equations (2) and (3).

[0018] vb = vi (2) vc = -vi (3)

The potential v at the connection point a between the resistors R1 and R3
a becomes as shown in the following Expression (4) from Expression (1) and Expression (2).

[0020]   va = [{(vb-va) / R1} + {(vc-va) / R3}] × Z       = [{(Vi-va) / R1} + {(-vi-va) / R3}] * Z                                                   … (4)

The equations (4) to va are as shown in the following equation (5).

[0022]   va = {(1 / R1)-(1 / R3)} vi / {(1 / Z) + (1 / R1)           + (1 / R3)} (5)

Since R1 = R3 (> 0) is set now, va = 0 from the equation (5).

On the other hand, assuming that the current flowing through the resistor R2 is I2, the relationship between the input voltage vi and the output voltage vo is given by the following equations (6) and (7).

[0025] vo = va + I2 (R1 + R2) (6) I2 = (vb-va) / R1 (7)

By substituting the equations (2) and (7) into the equation (6) and obtaining vo, the following equation (8) is obtained.

[0027]   vo = va + {(vi-va) / R1} × (R1 + R2) (8)

However, since va = 0 when R1 = R3 as described above, the closed gain of the amplifier circuit constituting the electronic circuit according to the embodiment of the present invention is expressed by the following equation (9). It becomes like

[0029]   vo / vi = (R1 + R2) / R1 (9)

As is apparent from the equation (9), the closed gain G becomes independent of the impedance Z, and the resistors R1 and R2 are
Therefore, when the amplifier circuit is actually constructed, an accurate closed gain that does not fluctuate with frequency can be obtained. Therefore, when the electronic circuit according to the embodiment of the present invention is used as the audio signal amplifier circuit, the sound quality can be improved.

Although the amplifier in the electronic circuit according to the embodiment of the present invention described above is the operational amplifier A1, another amplifier different from the operational amplifier may be used.

Further, in the electronic circuit according to the embodiment of the present invention described above, the gain of the inverting amplifier A2 is 1 and the resistance R1 = R3. However, the gain of the inverting amplifier A2 is n (n is a positive real number). ), And the resistance value of the resistor R3 is the resistance R1
The same applies when the resistance value of n is multiplied by n.

The electronic circuit according to the present invention will be described below with reference to another embodiment. FIG. 2 is a block diagram showing the configuration of an electronic circuit according to another embodiment of the present invention.

In an electronic circuit according to another embodiment of the present invention, as shown in FIG. 2, one end of a resistor R4 is connected to the output end of a non-inverting amplifier A4, and a signal current amplified by the non-inverting amplifier A4 is connected. To the resistor R4. On the other hand, an inverting amplifier A3 having a gain n is connected to the output end of the non-inverting amplifier A4, and the voltage at the output end of the non-inverting amplifier A4 is amplified by the inverting amplifier A3. The output terminal of the inverting amplifier A3 is connected to one end of a resistor R5 having a resistance value that is n times as high as the resistance value of the resistor R4, and the other end of the resistor R5 is connected to the other end of the resistor R4. Connected and configured.

Impedance Z1 due to resistance due to the pattern on the wiring board, wiring, etc. and reactance is equal to resistance R4.
Exists between the common connection point of the other end of the resistor R5 and the other end of the resistor R5 and the ground. In addition, in FIG. 2, E represents a DC power source,
A power supply voltage is supplied from the DC power supply E to the non-inverting amplifier A4 and the inverting amplifier A3 via a resistance on the wiring board, resistance due to wiring, etc. and impedance Z2 due to reactance.

In the electronic circuit according to another embodiment of the present invention described above, the signal current amplified by the non-inverting amplifier A4 flows through the resistor R4 based on the potential of the output terminal of the non-inverting amplifier A4, and this The current is affected and changes according to the change in impedance due to the change in frequency. However, the voltage based on the current flowing through the resistor R4 is inverted and amplified n times by the inverting amplifier A3, and
The resistance value of No. 4 flows into the resistor R5 having a resistance value of n times the gain of the inverting amplifier A3.

Therefore, also in the electronic circuit according to the other embodiment of the present invention, the voltage at the output end of the non-inverting amplifier A4 is n times the same as in the electronic circuit according to the one embodiment of the present invention. Because it is inverted and amplified, and the resistor R5
Since the resistance value of is set to n times the gain of the inverting amplifier of the resistance value of the resistor R4, the current due to the frequency variation in the current flowing through the impedance is canceled and is not affected by the frequency variation.

Since A4 is a non-inverting amplifier, A3 is an inverting amplifier, so that the currents supplied from the power supply lines change in opposite directions, so that they are supplied from the power supply line. The influence of the impedance Z2 existing in the power supply line can be suppressed even with respect to the change of the current. The same applies to the electronic circuit according to the embodiment of the present invention.

[0039]

As described above, according to the electronic circuit of the present invention, the current flowing in the impedance via the first resistor and the current flowing in the impedance via the second resistor due to the frequency fluctuation are , Beat each other,
The effect is that the signal current becomes independent of impedance and is not influenced by frequency.

Further, as described above, according to the electronic circuit of the present invention, when the electronic circuit is actually constructed,
The effect is that an accurate and accurate closed gain that does not fluctuate with frequency can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electronic circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an electronic circuit according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an amplifier circuit as a conventional electronic circuit.

[Explanation of symbols]

A1 operational amplifier A2 and A3 inverting amplifier A4 non-inverting amplifier R1, R2, R3, R4 and R5 resistors Z, Z1 and Z2 impedance

Claims (2)

(57) [Claims] 1. A first resistor through which a signal current flows, an inverting amplifier connected to one end of the first resistor, and a second resistor connected between the output end of the inverting amplifier and the other end of the first resistor. The electronic circuit is characterized in that the resistance value of the second resistance is set to the gain of the inverting amplifier multiplied by the resistance value of the first resistance. 2. An amplifier for amplifying an input voltage and a voltage divider circuit comprising a first resistor and a second resistor for dividing an output voltage of the amplifier are provided, one end of the second resistor being connected to the output end of the amplifier, and A common connection point of the first and second resistors is connected to the inverting input terminal of the amplifier, and a non-inverting amplifier circuit that applies the divided voltage applied to the second resistor to the inverting input terminal of the amplifier, and an inverting amplifier circuit It comprises an inverting amplifier for amplifying the voltage of the input terminal and a third resistor connected between the output end of the inverting amplifier and the non-common connection terminal of the first resistor, and the resistance value of the third resistor is set to the first value. An electronic circuit characterized in that the resistance value of the resistor is multiplied by the gain of the inverting amplifier.