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DESCRIPTION JPH09312525

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DESCRIPTION JPH09312525
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
analog amplifier circuit, and more particularly to an audio circuit which does not generate noise
due to a difference between reference potentials in an analog output signal sent to another
circuit system having different reference potentials. It relates to an amplification circuit.
[0002]
2. Description of the Related Art In recent years, electronic circuit systems have become
increasingly complex, and circuits are often formed on a plurality of substrates, and these
plurality of circuit systems are often connected by wiring. For this reason, when connecting
between the reference potentials (grounds) of the circuit systems on each substrate, a current
flows between the reference potentials, or the wiring becomes an antenna and noise is absorbed,
so that the reference potentials are different between different circuit systems. There are often
differences. Since this potential difference usually contains a very harmful noise component,
especially analog circuits will be greatly damaged.
[0003]
Also, in recent years, as the digitization of circuits has progressed, systems of mixed analog /
digital systems are increasing. Since digital circuits exchange signals with large amplitude pulses
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1
of 3 to 5 V, they generate large noise. In this case, the noise generated by the above-mentioned
mechanism becomes very large, and the degradation of the performance of the analog circuit
becomes remarkable. Therefore, how to prevent such noise from adversely affecting the analog
part has become very important.
[0004]
FIG. 15 shows a mechanism in which noise occurs between reference potentials (grounds) of two
circuit systems configured on different substrates. The arrows between the two circuits indicate
the direction of signal exchange. Assuming that a total current of I1 flows from the circuit system
1 to the circuit system 2 and a total of I2 flows from the circuit system 2 to the circuit system 1
during signal transfer, the reference potential between the two substrates A current of I 1 -I 2
flows from the circuit system 1 to the circuit system 2 in the connection line of Furthermore,
when this connection line plays the role of an antenna, a current In due to noise entering in the
form of radio waves also flows. Assuming that this reference potential connection line has an
impedance Z, the reference potential difference Vx between the two circuit systems is Vx = Z ×
(I2−I1 + In)
[0005]
In this equation, I1 and I2 are always generated at the time of signal exchange, and the system
becomes larger, and the larger the number of digital circuits, the larger. In addition, the amount
of unnecessary radiation increases due to an increase in digital circuits and an increase in the
reference potential connection line. The impedance Z also increases as the reference potential
connection line becomes longer. Therefore, it is considered that the larger the scale of the system
and the larger the digital part, the larger the reference potential difference Vx.
[0006]
Although the DC component of the reference potential difference Vx can be cut by the coupling
capacitor, the AC component is superimposed on the signal component at the time of delivery of
the analog signal, and the transmission performance is deteriorated.
[0007]
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In order to avoid this, a signal transfer circuit of a differential output type is conventionally used.
FIG. 14 shows an example of this signal transfer circuit. This circuit is provided at the output
stage of the circuit system 1 on the signal output side, and an amplifier circuit comprising
inverted analog amplifiers 1, 2 and 3 for generating differential signals eo + and eo− of the
signal ei1 to be transmitted It is provided at the input stage of the circuit system 2 on the input
side, and is constituted by a differential amplifier to which differential signals eo + and eo− are
input, and two signal lines for propagating the differential signal. By transmitting a signal at a
differential output and receiving a signal at a differential input, the noise component generated
due to the non-common reference potential is canceled. That is, assuming that R2 / R1 = 1 and
R21 / R11 = R22 / R12 = A in FIG. 14, the output potentials eo + and eo− of the circuit system 1
viewed from the reference potential 1 of the circuit system 1 are eo + = A × It becomes ei1, eo-=Axei1. Since eo + and eo− viewed from the differential amplifier of the circuit system 2 are
based on the reference potential 2 of the circuit system 2, eo + = A × ei1 + Vx and eo − = − A
× ei1 + Vx. Assuming that the gain of the differential amplifier of the circuit system 2 is A ′, the
output potential eo2 of the differential amplifier is eo2 = A ′ [(eo +) − (eo −)] = A ′ [(Aei1 +
Vx) − (− Aei1 + Vx) ] = A '× 2Aei1, and the noise Vx can be prevented from appearing at the
output potential eo2.
[0008]
However, in the conventional circuit, three output amplifiers and two signal lines are required on
the transmission side per channel, and on the other side, on the signal receiving side, amplifiers
of differential inputs are required. Cost and occupied area increase.
[0009]
An object of the present invention is, in view of the above-mentioned subject, to provide a circuit
which passes and receives a signal, without generating a noise ingredient, without almost
increasing cost and an occupied area.
[0010]
SUMMARY OF THE INVENTION In order to solve the above problems, the present invention
provides a first circuit system having an analog amplifier for amplifying a first signal based on a
first reference potential, and a first circuit. A second circuit system connected to the output end
of the analog amplifier of the system and amplifying an output signal of the analog amplifier
based on the second reference potential, and an input terminal connected to the second
reference potential of the second circuit system And a reference potential difference cancel
circuit in which the output signal is supplied to the input terminal of the analog amplifier
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together with the first signal, and the gain from the input terminal to the output terminal of the
analog amplifier is 1.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
FIG. 1 shows an embodiment of the present invention.
In the embodiment shown in FIG. 1, the circuit system 1 and the circuit system 2 are provided,
for example, on different substrates, and the reference potential of the circuit system 1 is
different from the reference potential of the circuit system 2 and analog signals from the circuit
system 1 to the circuit system 2 Shall be sent.
[0012]
The reference potential 1 of the circuit system 1 and the reference potential 2 of the circuit
system 2 are usually the lowest potential and are called ground.
Here, they are indicated by different ground potential marks. The reference potentials of the two
circuit systems are connected via an impedance Z. It is assumed that noise Vx is generated at
both ends of the impedance Z due to the above-mentioned reason.
[0013]
In the circuit system 1, the signal ei 1 is supplied to the input terminal of the analog amplifier 1
whose gain is A. An output signal of the analog amplifier 1 is transmitted to the circuit system 2.
When the reference potential difference cancel circuit 3 is not provided, the input signal of the
analog amplifier 2 of the circuit system 2 becomes A × ei1 + Vx with reference to the reference
potential 2 of the circuit system 2 and the difference Vx between the reference voltages of the
two circuit systems remains unchanged. It will be input to the circuit system 2. Therefore, a
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reference potential difference cancel circuit 3 with a gain of (1 / A) is provided in the circuit
system 1, its input terminal is connected to the ground point which is the reference potential 2 of
the circuit system 2, and the output signal of the reference potential difference cancel circuit is a
signal The signal is supplied to the input terminal of the analog amplifier 1 together with ei1.
[0014]
In this case, an output signal eo1 of the analog amplifier 1 based on the reference potential 1 of
the circuit system 1 is eo1 = A × ei1 + A × (1 / A) × (−Vx) = A × ei1−Vx. The input signal ei2
of the analog amplifier 2 with reference to the reference potential 2 of the circuit system 2 is ei2
= A × ei1−Vx + Vx, and the noise component Vx can be removed.
[0015]
FIG. 2 shows an embodiment of the present invention in which an inverting amplifier is used for
the analog amplifier 1 shown in FIG. In the circuit system 1, the signal ei1 is supplied to the
inverting input terminal of the operational amplifier 21 via the resistor R1, and the inverting
input terminal of the operational amplifier 21 is connected to the output terminal of the
operational amplifier 21 via the resistor R2. The output terminal of the operational amplifier 21
is connected to the input terminal of the analog amplifier 2 of the circuit system 2. The reference
potential of the circuit system 2 is connected to the input terminal IN of the reference potential
difference cancel circuit 3 of the circuit system 1. The reference potential difference canceling
circuit 3 is a voltage dividing circuit using a resistor, and a resistor R3 and a resistor R4 are
connected in series between the input terminal IN of the reference potential difference canceling
circuit 3 and the reference potential 1 of the circuit system 1 The connection point of the resistor
R4 is the output terminal OUT of the reference potential difference cancel circuit 3. The output
terminal OUT of the reference potential difference cancel circuit 3 is connected to the noninverting input terminal of the operational amplifier 21.
[0016]
In this embodiment, the gain A− of the analog amplifier 1 viewed from the inverted input signal
of the analog amplifier 1 is A − = − R2 / R1, and the gain of the analog amplifier 1 viewed from
the non-inverted input signal of the analog amplifier 1 A + becomes A + = (R1 + R2) / R1.
Accordingly, if R4 / R3 = R1 / R2 in the reference potential difference cancel circuit 3, the gain
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from the input terminal IN of the reference potential difference cancel circuit 3 to the output
terminal of the analog amplifier 1 becomes one. In this case, the output potential eo1 of the
analog amplifier 1 based on the reference potential 1 of the circuit system 1 is eo1 = (− R2 / R1)
× ei1−Vx. Therefore, input potential ei2 of analog amplifier 2 based on reference potential 2 of
circuit system 2 becomes ei2 = (-R2 / R1) .times.ei1-Vx + Vx = (-R2 / R1) .times.ei1, and cancels
noise Vx be able to.
[0017]
FIG. 3 shows an embodiment of the present invention in the case of using an inverting input type
amplifier as the analog amplifier 1 and using a single power supply. The analog amplifier 1 of
this embodiment is the same as the analog amplifier shown in FIG. 2 including the operational
amplifier 21 and the resistors R1 and R2. The signal ei1 is supplied to the inverting input
terminal of the operational amplifier 21 via the resistor R1, and the output terminal of the
operational amplifier 21 is connected to the input terminal of the analog amplifier 2 of the circuit
system 2 via the coupling capacitor C1. On the other hand, the reference potential of the circuit
system 2 is connected to the input terminal IN of the reference potential difference cancel circuit
3 of the circuit system 1 via the coupling capacitor C2. The reference potential difference cancel
circuit 3 includes a resistor R3 and a resistor R4 connected in series between the power supply
potential of the circuit system 1 (indicated by VDD in the figure) and the reference potential, an
input terminal IN of the reference potential difference cancel circuit 3 and resistors R3 and R4.
And a resistor R5 provided between the connection points of The connection point between the
resistors R3 and R4 serves as the output terminal OUT of the reference potential difference
cancel circuit 3 and is connected to the non-inverted input terminal of the operational amplifier
21.
[0018]
In the embodiment shown in FIG. 2, since the input signal ei1 of the analog amplifier 1 swings
around the ground which is the reference potential, two power supplies of plus and minus are
required for the analog amplifier. When only a single power supply is used as in the present
embodiment, the signal can not be shaken with reference to the ground, so it is necessary to
generate a reference potential Vref for the signal separately from the ground. Vref is normally set
to half the power supply potential. In this case, the input signal ei1 of the analog amplifier 1 is
ei1 = es + Vref. Here, es is an input signal and normally does not include a DC component, and
the amplitude of ei1 swings around Vref. The reference potential difference cancel circuit 3
shown in FIG. 3 doubles as a Vref generation circuit. Vref is a DC value, which is generated by
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dividing the voltage between the power supply potential and the reference potential with the
resistors R3 and R4. However, when the power supply potential is unstable, a method of creating
a constant potential and dividing it by the resistors R3 and R4 is also conceivable.
[0019]
Unlike the embodiment shown in FIG. 2, the input terminal IN of the reference potential
difference cancel circuit 3 shown in FIG. 3 is connected to the reference potential of the circuit
system 2 via the coupling capacitor C2. Therefore, only the AC component of the noise Vx is
input to the reference potential difference cancel circuit 3. Therefore, although the DC
component of the noise Vx is not canceled, in the case of a single power supply, the output
terminal of the analog amplifier 1 and the input terminal of the analog amplifier 2 are connected
via the coupling capacitor C1. There is no need to cancel the DC component. The gain of the
reference potential difference cancel circuit 3 with respect to the AC component of Vx can be
similarly obtained by replacing the resistor R4 in FIG. 2 with a parallel connection of the resistors
R3 and R4. Assuming that the resistance value of this parallel connection is R4 ′, R4 ′ = R3 ×
R4 / (R3 + R4), and to cancel the noise, R4 ′ / (R4 ′ + R5) = 1 / (A +) = R1 / (R1 + R2) may be
established. Therefore, if R4 '/ R5 = R1 / R2 (R3 × R4) / [(R3 + R4) × R5] = R1 / R2, the AC
component of the noise Vx is canceled as in the case shown in FIG. it can.
[0020]
FIG. 4 shows an embodiment of the present invention in the case of using a non-inverting
amplifier as an analog amplifier. In the present embodiment, the signal ei1 is supplied to the noninverting input terminal of the operational amplifier 41, and the output terminal of the
operational amplifier 41 is connected to the input terminal of the analog amplifier 2 of the circuit
system 2. Further, the reference potential of the circuit system 2 is connected to the input
terminal IN of the reference potential difference cancel circuit 3. In the reference potential
difference cancel circuit 3, the input terminal IN of the reference potential difference cancel
circuit 3 is connected to the inverting input terminal of the operational amplifier 42 through the
resistor R3, and the inverting input terminal of the operational amplifier 42 is through the
resistor R4. Connected to the output terminal. The noninverting input terminal of the operational
amplifier 42 is connected to the reference potential of the circuit system 1. The operational
amplifier 42 plays the role of a buffer amplifier that outputs a low impedance of Vx multiplied by
(-R4 / R3) to the output terminal OUT of the reference potential difference cancellation circuit 3.
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[0021]
Here, assuming that the gain A− of the analog amplifier 1 viewed from the inverted input signal
of the analog amplifier 1 is A − = − R2 / R1R4 / (R4 + R5) = R1 / R2, from the input terminal IN
of the reference potential difference cancel circuit 3 The gain to the output terminal of the
analog amplifier 1 is one. As a result, eo1 = ei1 × (R1 + R2) / R1−Vxei2 = eo1 + Vx = ei1 × (R1
+ R2) / R1 and the noise Vx can be prevented from appearing in the input signal ei2 of the
analog amplifier 2.
[0022]
FIG. 5 shows an embodiment in which the circuit shown in FIG. 4 is operated by a single power
supply. In the embodiment shown in FIG. 5, the non-inverted amplifier shown in FIG. The signal
ei1 is supplied to the noninverting input terminal of the operational amplifier 51, and the
inverting input terminal of the operational amplifier 51 is connected to the output terminal OUT
of the reference potential difference cancel circuit 3 via the resistor R1 and the operational
amplifier via the resistor R2. It is connected to the 51 output terminal. The output terminal of the
operational amplifier 51 is connected to the input terminal of the analog amplifier 2 of the circuit
system 2 via the coupling capacitor C1. Further, the input terminal IN of the reference potential
difference cancel circuit 3 is connected to the reference potential of the circuit system 2 through
the coupling capacitor C2. In the reference potential difference cancel circuit 3, the input
terminal IN of the reference potential difference cancel circuit 3 is connected to the inverting
input terminal of the operational amplifier 52 through the resistor R3, and the inverting input
terminal of the operational amplifier 52 is the operational amplifier 52 through the resistor R4.
Connected to the output terminal of The non-inverting input terminal of the operational amplifier
52 is connected to another reference potential Vref having a constant potential difference with
respect to the reference potential of the circuit system 1. As described in the description of FIG.
3, the Vref may be generated by dividing the power supply potential VDD and the reference
potential by resistance or may be supplied from a constant voltage source.
[0023]
Also in the present embodiment, the AC component of Vx can be canceled by satisfying the
equation shown in the embodiment shown in FIG. That is, assuming that R3 / R4 = R1 / R2, the
gain from the input terminal IN of the reference potential difference cancel circuit 3 to the output
terminal of the analog amplifier 1 becomes 1, and noise of the input signal of the analog
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amplifier 2 can be canceled. In this embodiment, as in the embodiment shown in FIG. 3, the
reference potential difference cancel circuit 3 doubles as a Vref generation circuit.
[0024]
FIG. 6 shows an embodiment of the present invention in which a differential amplifier is used as
the analog amplifier 1. In the present embodiment, the signal ei- is supplied to the inverting input
terminal of the operational amplifier 61 via the resistor R1, and the inverting input terminal of
the operational amplifier 61 is connected to the output terminal of the operational amplifier 61
via the resistor R2. Also, the signal ei + is supplied to the non-inverted input terminal of the
operational amplifier 61 via the resistor R3. The output terminal of the operational amplifier 61
is connected to the input terminal of the analog amplifier 2 of the circuit system 2. On the other
hand, the reference potential of the circuit system 2 is connected to the input terminal IN of the
reference potential difference cancel circuit 3. The reference potential difference cancel circuit 3
includes resistors R4 and R5 connected in series between the input terminal IN and the reference
potential 1 of the circuit system 1. The connection point between the resistors R 4 and R 5 is the
output terminal OUT of the reference potential difference cancel circuit 3 and is connected to the
non-inverted input terminal of the operational amplifier 61.
[0025]
In this embodiment, the output signal eo1 of the analog amplifier 1 is eo1 = (ei +) × R4 × (R1 +
R2) / [(R3 + R4 ′) × R1] − (ei−) × R2 / R1. ここで、R4’=R4×R5/(R4+R5)
[0026]
The gain A + of the analog amplifier 1 viewed from the non-inverted input signal is A + = (R1 +
R2) / R1 as in the case shown in FIG. Further, the gain A ′ from the input terminal IN to the
output terminal OUT of the reference potential difference cancel circuit 3 is A ′ = R3 ′ / (R3 ′
+ R4). ここで、R3’=R3×R5/(R3+R5)である。 A’=1/(A+)とすれば
Vxをキャンセルすることができるので、
R3’/(R3’+R4)=R1/(R1+R2)R3’/R4=R1/R2R3×R5/[(
R3+R5)×R4]=R1/R2とすれば、Vxをキャンセルすることができる。
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[0027]
FIG. 7 shows an embodiment in which the circuit shown in FIG. 6 is operated by a single power
supply. In the embodiment shown in FIG. 7, the differential analog amplifier is the same as the
differential analog amplifier shown in FIG. The output terminal of the operational amplifier 71 is
connected to the input terminal of the analog amplifier 2 of the circuit system 2 via the coupling
capacitor C1. The reference potential of the circuit system 2 is connected to the input terminal IN
of the reference potential difference cancel circuit 3 via the coupling capacitor C2. The reference
potential difference cancel circuit 3 is connected between a connection point of the resistors R4
and R5 connected in series between the power supply potential of the circuit system 1 and the
reference potential and the resistors R4 and R5 and the input terminal IN of the reference
potential difference cancel circuit 3. The connection point of the resistors R4 and R5 serves as
the output terminal OUT of the reference potential difference cancel circuit 3 and is connected to
the non-inverted input terminal of the operational amplifier 71.
[0028]
In this embodiment, by replacing R4 of the embodiment shown in FIG. 6 with R4 × R5 / (R4 +
R5), the condition of the resistance for canceling Vx can be obtained. The reference potential
difference cancel circuit 3 of the present embodiment doubles as a Vref generation circuit as in
the embodiments shown in FIGS. 3 and 5.
[0029]
FIG. 8 shows an embodiment in which a line connecting the input terminal IN of the reference
potential difference cancel circuit 3 and the reference potential 2 of the circuit system 2 is
shared when there are two channels of the circuit shown in FIG.
[0030]
In this embodiment, two analog amplifiers similar to those in FIG. 3 and two reference potential
difference cancel circuits 3 are provided in the circuit system 1, and the output signals of the
respective analog amplifiers 1a and 1b are respectively connected via coupling capacitors C1a
and C1b. It is supplied to the input analog amplifiers 2a and 2b of the circuit system 2.
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On the other hand, the input terminal IN of the reference potential difference cancel circuit 3 of
each circuit is connected to the reference potential 2 of the circuit system 2 via the common
coupling capacitor C2. As described above, in the present embodiment, the capacitor C2 for
cutting the DC component can be made one, and the number of parts of the circuit can be
reduced. Furthermore, even when there are three or more channels, the input signal line of the
reference potential difference cancel signal can be made common.
[0031]
Further, although the embodiment shown in FIG. 8 is a case of a single power supply, similarly in
the case of a dual power supply as in the embodiment shown in FIG. 2, similarly between
reference potential difference of reference potential difference cancel circuit 3 and circuit system
2 Connection lines can be made common.
[0032]
FIG. 9 shows an embodiment in which the input signal line of the reference potential difference
cancel circuit 3 is made common as in the embodiment shown in FIG. 8 when the circuit shown
in FIG. 5 has two channels.
In this embodiment, two analog amplifiers similar to those in FIG. 5 and two reference potential
difference cancel circuits 3 are provided in the circuit system 1, and the output signals of the
respective analog amplifiers 1a and 1b are respectively connected via coupling capacitors C1a
and C1b. As well as being supplied to the input amplifiers 2a and 2b of the circuit system 2, the
input terminals IN of the two reference potential difference cancel circuits 3 are connected to the
reference potential 2 of the circuit system 2 via a common capacitor C2. In the present
embodiment, as in the embodiment shown in FIG. 8, the number of parts of the circuit can be
reduced. Furthermore, even when there are three or more channels, the input signal lines of the
reference potential difference cancel circuit 3 can be shared in the same manner.
[0033]
Further, although the embodiment shown in FIG. 9 is a case of a single power supply, similarly in
the case of a dual power supply as shown in FIG. 4, similarly between the input terminal of
reference potential difference cancel circuit 3 and the reference potential of circuit system 2
Connection lines can be made common.
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[0034]
FIG. 10 shows an embodiment in which the reference potential difference cancel circuit 3 of both
circuits is shared when there are two channels of the circuit shown in FIG.
In the circuit system 1, one reference potential difference cancel circuit 3 identical to that shown
in FIG. 3 is provided, and two inverting analog amplifiers 1a and 1b identical to those shown in
FIG. 3 are provided. The output signals of the analog amplifiers 1a and 1b are supplied to the
input amplifiers 2a and 2b of the circuit system 2 via coupling capacitors C1a and C1b,
respectively, and the input terminal IN of the reference potential difference cancel circuit 3 is
coupled via a coupling capacitor C2. The reference potential 2 of the circuit system 2 is
connected, and the output terminal OUT of the reference potential difference cancel circuit 3 is
connected to the non-inverted input terminals of the two analog amplifiers 1a and 1b. In the
present embodiment, the number of parts can be further reduced as compared with the
embodiment shown in FIG. Furthermore, even when there are three or more channels, the
reference potential difference cancel circuit 3 can be commonly used.
[0035]
Further, although the embodiment shown in FIG. 10 is the case of a single power supply, the
reference potential difference cancel circuit 3 can be shared in the case of two power supplies as
shown in FIG. FIG. 11 shows an embodiment in which the reference potential difference cancel
circuit 3 of both circuits is shared when there are two channels of the circuit shown in FIG. In the
circuit system 1, one reference potential difference cancel circuit 3 identical to that shown in FIG.
5 is provided, and two non-inverted analog amplifiers 1a and 1b identical to those shown in FIG.
5 are provided. There is. Output signals of the analog amplifiers 1a and 1b are supplied to input
amplifiers 2a and 2b of the circuit system 2 through coupling capacitors C1a and C1b,
respectively. The input terminal IN of the reference potential difference cancel circuit 3 is
connected to the reference potential 2 of the circuit system 2 via the coupling capacitor C2, and
the output terminal OUT of the reference potential difference cancel circuit 3 is connected to the
inverting input terminal of the two operational amplifiers. It is connected via the resistors R1a
and R1b. In the present embodiment, the number of parts can be further reduced as compared
with the embodiment shown in FIG. Furthermore, even when there are three or more channels,
the reference potential difference cancel circuit 3 can be commonly used.
[0036]
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12
Further, although the embodiment shown in FIG. 11 is the case of a single power supply, the
reference potential difference cancel circuit 3 can be shared in the case of two power supplies as
shown in FIG. FIG. 12 shows an embodiment of the present invention used using an analog
amplifier and a switched capacitor. In this embodiment, the resistors R1 and R2 connected to the
amplifier of the embodiment shown in FIG. 2 are replaced by switched capacitors. As shown in
FIG. 13, in the switched capacitor, a capacitor C, a movable contact is connected to a first
terminal of the capacitor C, a fixed contact is connected to a terminal a and a reference potential,
and a movable contact is a capacitor The fixed contact is connected to the second terminal of C,
and the fixed contact is constituted by the terminal b and the switch SWb connected to the
reference potential. This switched capacitor circuit can be considered to be equivalent by the
relationship between the resistor R and the following equation as shown in FIG.
[0037]
T / C = R Here, T is a switching cycle of SWa and SWb. This equation holds when the frequency
of the signal is sufficiently low relative to f = 1 / T. SW1 to SW1 in FIG. 12 correspond to R1 in
FIG. 2, and SW2 to SW3 in FIG. 12 correspond to R2 in FIG. Even in a circuit using a switched
capacitor, the present invention can provide the same effect as a circuit using a resistor.
[0038]
As described above, according to the present invention, by using one analog amplifier and a
simple reference potential difference canceling circuit, it is not necessary to transmit and receive
signals using differential signals. This eliminates the need for an amplifier that generates a signal
and an amplifier that receives a differential signal, thereby reducing the cost and the area
occupied by the circuit.
[0039]
Further, according to the present invention, when operating the amplifier with a single power
supply, the increase in the number of parts can be made small by combining the reference
potential difference cancel circuit and the Vref generation circuit.
[0040]
Furthermore, according to the present invention, when there are a plurality of signal channels,
the number of signal lines can be reduced to half as compared with the prior art by making the
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input lines of the reference potential difference cancel circuit common, circuit complexity and It
is possible to prevent an increase in occupied area and an increase in cost.
[0041]
Further, according to the present invention, when there are a plurality of signal channels, not
only can the signal line be halved as compared with the prior art, but the number of parts can be
significantly reduced by making the reference potential difference cancel circuit common. it can.
This prevents the circuit from becoming complicated, reduces the area occupied by the circuit,
and reduces the cost.
[0042]
Brief description of the drawings
[0043]
1 shows an embodiment of the present invention.
[0044]
2 is a diagram showing an embodiment of the present invention using an inverting amplifier.
[0045]
3 is a diagram showing an embodiment of the present invention using a single power supply
inverting amplifier.
[0046]
4 is a diagram showing an embodiment of the present invention using a non-inverting amplifier.
[0047]
5 is a diagram showing an embodiment of the present invention using a single-supply forward
rotation type amplifier.
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[0048]
6 is a diagram showing an embodiment of the present invention using a differential amplifier.
[0049]
7 is a diagram showing an embodiment of the present invention using a single power supply
differential amplifier.
[0050]
8 is a diagram showing an embodiment of the present invention using an inverting amplifier.
[0051]
7 is a diagram showing an embodiment of the present invention using a non-inverting amplifier.
[0052]
8 is a diagram showing an embodiment of the present invention in which the input line of the
reference potential difference cancel circuit is shared by using an inverting amplifier.
[0053]
9 is a diagram showing an embodiment of the present invention in which the input line of the
reference potential difference cancel circuit is common using a non-inverting amplifier.
[0054]
10 is a diagram showing an embodiment of the present invention in which the reference
potential difference cancel circuit is common using an inverting amplifier.
[0055]
11 is a diagram showing an embodiment of the present invention in which the reference
potential difference cancel circuit is common using a non-inverting amplifier.
[0056]
12 is a diagram showing an embodiment of the present invention using a switched capacitor for
the inverting amplifier.
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[0057]
13 is a diagram showing the equivalent relationship between the switched capacitor and the
resistor.
[0058]
14 is a diagram showing the prior art.
[0059]
152 is a diagram for explaining the mechanism of generating a reference potential difference
between the two circuit systems.
[0060]
Explanation of sign
[0061]
Analog amplifier 1 ... Analog amplifier that transmits a signal, analog amplifier 2 ... Analog
amplifier that receives a signal, reference potential difference cancellation circuit ... Reference
potential difference cancellation circuit, reference potential 1 ... Reference potential of circuit
system 1, reference potential 2 ... Circuit system 2 Reference potential Z: impedance between
reference potential 1 and reference potential 2 Vx: noise generated in impedance Z
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