JP2008092310A - Voltage control current source circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage controlled current source which converts an input signal to a current and supplies it as a differential current source. <P>SOLUTION: A differential voltage generation circuit 110 converts an input voltage Vin to differential voltages V1 and V2, and then inputs them into a first variable current source 132 and a second variable current source 136 respectively. The first variable current source 132 is connected between a first output terminal 104 and a ground voltage, and changes an output current corresponding to the voltage V1. The second variable current source 136 that has the same structure as the first variable current source 132 is connected between a second output terminal 106 and the ground voltage, and changes an output current I4 corresponding to the voltage V2. A first constant current source 122 is connected between a power supply VDD and the first output terminal 104, and outputs a constant current I1. A second constant current source 126 is connected between the power supply VDD and the second output terminal 106, and outputs a constant current I2. A differential current between the current I1 and a current I3 is outputted from the first output terminal 104, and a differential current between the currents I2 and I4 is outputted from the second output terminal 106. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a voltage controlled current source circuit, and more particularly to a voltage controlled current circuit that converts a single input voltage into a differential current and outputs the differential current.

  In a device that handles sound, in order to improve the balance and reduce noise, an input signal that becomes a single voltage signal is often converted into a differential signal.

For example, in the digital amplifier disclosed in Patent Document 1, an input signal is converted into a differential signal.
JP 2005-303814 A

  As described in Patent Document 1, when a digital amplifier converts an input signal into a differential voltage signal to form a differential voltage source, the digital amplifier requires an integration amplifier composed of an operational amplifier and a capacitive element. There is a problem that power consumption is large.

  Therefore, it is desired to convert an input signal into a current and provide it as a differential current source.

  One aspect of the present invention is a voltage-controlled current source that converts a voltage input from an input terminal into a differential current and outputs the differential current from the first output terminal and the second output terminal. The voltage controlled current source includes a differential voltage generation circuit, a first constant current source, a second constant current source, a first variable current source, and a second variable current source.

  The differential voltage generation circuit converts a voltage input from the input terminal into a differential voltage and outputs a first voltage and a second voltage.

  The first constant current source is connected between the first output terminal and the first power source, and the second constant current source is connected between the second output terminal and the first power source. Has been. The two constant current sources provide the same constant current.

  The first variable current source is connected between the first output terminal and a second power source different from the first power source, and according to the first voltage input from the differential voltage generation circuit. Variable output current. The second variable current source has the same configuration as the first variable current source. The second variable current source is connected between the second output terminal and the second power supply, and varies the output current according to the second voltage input from the differential voltage generation circuit.

  With such a configuration, a difference current between the output currents of the first constant current source and the first variable current source is output from the first output terminal, and the second constant current source is output from the second output terminal. A differential current of the output current of the second variable current source is output, and a differential current is provided.

  An expression of the present invention as a method or system is also effective as an aspect of the present invention.

  According to the technology of the present invention, a single input voltage signal can be converted into a differential current source and provided.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
FIG. 1 is a schematic diagram of a voltage controlled current source 100 according to the first embodiment of the present invention. The voltage control current source 100 includes a differential voltage generation circuit 110 that converts an input voltage Vin into differential voltages V1 and V2, a first constant current source 122, a second constant current source 126, and a first variable current. A source 132 and a second variable current source 136 are provided.

  The voltage-controlled current source 100 has an input terminal 102 and two output terminals, that is, a first output terminal 104 and a second output terminal 106, and an input voltage Vin is input from the input terminal 102, and from the two output terminals. A current CSP and a current CSN are output, respectively.

  The first constant current source 122 is connected between the power supply VDD and the first variable current source 132, and provides a constant current I1. The second constant current source 126 is connected between the power supply VDD and the second variable current source 136, and provides the same constant current I2 as the constant current I1.

  The first variable current source 132 is connected between the first constant current source 122 and the ground voltage, and the second variable current source 136 is connected between the second constant current source 126 and the ground voltage. . The first variable current source 132 receives a voltage V1 that is one of the differential voltages generated by the differential voltage generation circuit 110, and the second variable current source 136 receives the other differential voltage. A voltage V2 is input.

  The first variable current source 132 varies the output current I3 according to the input voltage V1. The second variable current source 136 has the same configuration as that of the first variable current source 132, and varies the output current I4 according to the input voltage V2. Since the voltage V1 and the voltage V2 input to the first variable current source 132 and the second variable current source 136 are differential voltages, the current I3 and the current I4 have a relationship of (I3 = −I4), They are out of phase with each other.

  The first output terminal 104 is connected to the current dividing point 112 between the first constant current source 122 and the first variable current source 132. That is, the current CSN output from the first output terminal 104 is a difference current between the current I1 and the current I3. Since the current I3 is variable according to the voltage V1, the current CSN output from the first output terminal 104 is also variable according to the voltage V1.

  The second output terminal 106 is connected to the current dividing point 116 between the second constant current source 126 and the second variable current source 136. The current CSP output from the second output terminal 106 is a difference current between the currents I2 and I4. Since the current I4 is variable according to the voltage V2, the current CSP output from the second output terminal 106 is also variable.

  FIG. 2 shows a detailed configuration of the voltage controlled current source 100. In the figure, the bias current IBIAS, the plurality of transistors (N-type transistors N1 and N2, P-type transistors P1 to P7), the operational amplifier OP3, and the resistors RC1 and RC2 are the same as those of the first constant current source 122 shown in FIG. The constant current source 126 is configured, and a constant current I1 and a constant current I2 are generated by them.

  The differential voltage generation circuit 110 converts the input voltage Vin input from the input terminal 102 into differential voltages V1 and V2. As illustrated, the differential voltage generation circuit 110 includes a resistor Rin1, a resistor RF1, an operational amplifier OP1, a resistor Rin2, a resistor RF2, and an operational amplifier OP2. One end of the resistor Rin1 is connected to the input terminal 102, and the other end is connected to the inverting terminal of the operational amplifier OP1.

  One end of the resistor RF1 is connected between the inverting terminal of the operational amplifier OP1 and the resistor Rin1, and the other end of the resistor RF1 is connected to the second variable current source 136. The voltage output from the other end of the resistor RF1 is the voltage V2 input to the second variable current source 136.

  The operational amplifier OP1 has an inverting terminal connected to the resistor Rin1 and a non-inverting terminal connected to the reference voltage Vcom. The output is connected to one end of the resistor Rin2. The other end of the resistor RF1 is also connected between the operational amplifier OP1 and the resistor Rin2. As a result, the voltage V2 is also input to the resistor Rin2.

  The resistor Rin, the resistor RF1, and the operational amplifier OP1 constitute an inverting amplifier circuit. By this inverting amplifier circuit, the input voltage Vin is inverted and amplified and output as the voltage V2.

  The resistor Rin2, the resistor RF2, and the operational amplifier OP2 also constitute an inverting circuit. The voltage V2 input to the resistor Rin2 of the inverting circuit is inverted to become the voltage V1, and is input to the first variable current source 132 from one end of the resistor RF2.

  In this way, the differential voltage generation circuit 110 converts the input voltage Vin, which is a single signal, into a differential voltage composed of V1 and V2.

  The first variable current source 132 and the second variable current source 136 have the same configuration except that the input voltages are opposite in phase to each other. Therefore, only the first variable current source 132 is described in detail here. Will be explained.

  FIG. 3 shows a configuration of the first variable current source 132 cut out from the voltage controlled current source 100 shown in FIG. The first variable current source 132 converts the input voltage V1 into a current I3, and includes an N-type transistor N3, a first resistor RSN, a second resistor RDN, a third resistor RGN, and an operational amplifier OP4. Prepare.

  The drain of the N-type transistor N3 is connected to the P-type transistor P5 of the constant current source that outputs the constant current I1, and the source is connected to one end of the first resistor RSN. Note that the other end of the first resistor RSN is connected to the ground potential. The gate of the N-type transistor N3 is connected to the output of the operational amplifier OP4.

  The operational amplifier OP4 has an inverting terminal connected between the N-type transistor N3 and the first resistor RSN, and a non-inverting terminal connected between the second resistor RDN and the third resistor RGN connected in series. Yes.

  One end of the second resistor RDN is input with the voltage V1 from the differential voltage generation circuit 110, and the other end is connected to the third resistor RGN.

  The third resistor RGN has one end connected to the second resistor RDN and the other end connected to the ground voltage.

  The first output terminal 104 of the voltage controlled current source 100 is connected to a current dividing point 112 between the N-type transistor N3 and the P-type transistor P5 of the constant current source. Note that the current direction of the current dividing point 112 and the first output terminal 104 flows from the current dividing point 112 to the first output terminal 104 or from the first output terminal 104 to the current dividing point 112. However, for the convenience of explanation, the expression “flowing from the current dividing point 112 to the first output terminal 104” is used in any case.

  A current flowing between the current dividing point 112 and the first variable current source 132 is I3. As illustrated, since the current I1 is a constant current, the current CSN flowing from the current dividing point 112 to the first output terminal 104 varies according to the current I3.

  The current I3 is controlled by the voltage input to the gate of the N-type transistor N3. This voltage is the output of the operational amplifier OP4.

  The voltage V1 input to the first variable current source 132 from the differential voltage generation circuit 110 is divided by the second resistor RDN and the third resistor RGN, and “V1 × RGN” is applied to the non-inverting terminal of the operational amplifier OP4. / (RDN + RGN) "is input. That is, when the voltage V1 increases, the voltage input to the operational amplifier OP4 also increases, and the current I3 increases accordingly.

  With such a configuration, the current I3 flowing through the N-type transistor N3 is controlled by the voltage V1.

  The same applies to the second variable current source 136, and the current I4 flowing through the N-type transistor N4 is controlled by the voltage V2 having a phase opposite to that of the voltage V1.

  Since the voltages V1 and V2 input to the first variable current source 132 and the second variable current source 136 are differential voltages, the currents I3 and I4 are opposite-phase differential currents.

  Then, the current CSP and the current CSN that are the outputs of the voltage control current source 100 are differential currents that vary according to the currents I3 and I4.

  The current CSP and the current CSN are controlled by the voltage V1 and the voltage V2 input to the first variable current source 132 and the second variable current source 136. The voltage V1 and the voltage V2 are generated from the input voltage Vin. Therefore, the output current CSP and the current CSN are controlled by the input voltage Vin.

  In this way, the voltage controlled current source 100 can obtain the differential currents CSP and CSN from the input voltage Vin that is a single voltage signal, and can contribute to the suppression of power consumption in audio equipment and the like.

  In the present embodiment, the first variable current source 132 does not directly input the voltage V1 to the gate of the N-type transistor N3, but provides feedback control by providing an operational amplifier OP4 between the N-type transistor N3 and the voltage V1. Is going. By doing so, it is possible to prevent the element noise of the N-type transistor N3 from being output as it is to the current CSN. Since the noise in this case becomes the input conversion noise (1 / gain of the operational amplifier OP4) of the operational amplifier OP4 smaller than the element noise of the N-type transistor N3, the noise of the current CSN can be suppressed.

  Similarly, the second variable current source 136 can also suppress CSP noise to input equivalent noise of the operational amplifier OP5.

<Second Embodiment>
FIG. 4 shows a configuration of a voltage controlled current source 200 according to the second embodiment of the present invention.
In the illustrated voltage controlled current source 200, the resistor Rin and the operational amplifier OP1 generate a differential voltage generation circuit, whereby the input voltage Vin input via the input terminal 202 is converted into differential voltages V1 and V2. .

  In the figure, a bias current IBIAS, a power supply VDD, a ground potential, and a plurality of transistors (N-type transistors N1, N2 and N6, P-type transistors P1 to P10) constitute three constant current sources, and each P-type transistor. A constant current I1, a constant current I2, and a constant current I5 are output from P5, P-type transistor P7, and P-type transistor P10.

  Further, the P-type transistors P11 and P12, the N-type transistors N3 and N7, and the N-type transistors N4 and N8 constitute two variable current sources in the voltage-controlled current source 200 of the present embodiment. Details thereof will be described below.

  The P-type transistor P11 and the P-type transistor P12 constitute a differential pair, and the P-type transistor P10 is connected to the differential pair. The differential voltages V1 and V2 from the operational amplifier OP1 are input to the gates of the P-type transistors P11 and P12, respectively. Since the constant current I5 is output from the P-type transistor P10 and the voltages V1 and V2 are differential voltages, the currents flowing through the P-type transistor P11 and the P-type transistor P12 become the differential currents I6 and I7.

  A circuit block 242 and a circuit block 246 are connected to the output terminals of the P-type transistors P11 and P12, respectively.

  The circuit block 242 includes N-type transistors N3 and N7. N-type transistor N7 is connected between P-type transistor P12 and ground potential, and N-type transistor N3 is connected between P-type transistor P5 and ground potential. The gate of the N-type transistor N3 and the gate of the N-type transistor N7 are connected. That is, the circuit block 242 is a current mirror, whereby the same current I3 as the current I6 flowing through the N-type transistor N7 flows through the N-type transistor N3.

  Similarly to the circuit block 242, the circuit block 246 is a current mirror composed of N-type transistors N4 and N8, whereby the same current I4 as the current I7 flowing through the N-type transistor N8 flows through the N-type transistor N4. It will be.

  A current dividing point 212 between the P-type transistor P5 and the N-type transistor N3 is connected to the first output terminal 204 of the voltage controlled current source 200. As described above, the constant current I1 flows from the P-type transistor P5. Since the current flowing from the current dividing point 212 to the first output terminal 204, that is, the output current CSN is a difference current between the current I1 and the current I3, it fluctuates according to the current I3 flowing through the N-type transistor N3.

  Similarly, the output current CSP flowing from the current dividing point 216 to the second output terminal 206 varies according to the current I4 flowing through the N-type transistor N4.

  Since the currents I6 and I7 are differential currents, the currents I3 and I4 are also differential currents. Accordingly, the output currents CSP and CSN are also differential currents.

  The N-type transistor N7 of the circuit block 242 also forms a current mirror with the N-type transistor N5, whereby the current flowing through the N-type transistor N7 is fed back to the operational amplifier OP1.

  As described above, the voltage-controlled current source 200 according to the present embodiment obtains the differential current CSP and the current CSN from the input voltage Vin that is a single voltage signal, and contributes to the suppression of power consumption in audio equipment and the like. Can do.

<Third Embodiment>
In the two embodiments described above, the power supply VDD, the constant current source, the variable current source, and the ground voltage are connected in the order of connection. The ground voltage, the constant current source, the variable current source, and the power supply VDD are connected in the order of connection. The voltage controlled current source of the present invention can also be realized. Here, as an example, the connection order in the voltage controlled current source shown in FIG.

  FIG. 5 shows a configuration of a voltage controlled current source 300 according to the third embodiment of the present invention. The voltage control current source 300 includes a differential voltage generation circuit 310 that converts the input voltage Vin into differential voltages V1 and V2, a first constant current source 322, a second constant current source 326, and a first variable. A current source 332 and a second variable current source 336 are provided.

  The voltage-controlled current source 300 has an input terminal 302 and two output terminals, that is, a first output terminal 304 and a second output terminal 306. The input voltage Vin is input from the input terminal 302, and the two output terminals are used. Currents CSP and CSN are output, respectively.

  The first constant current source 322 is connected between the ground voltage and the first variable current source 332, and provides a constant current I1. The second constant current source 326 is connected between the ground voltage and the second variable current source 336 and provides the same constant current I2 as the constant current I1.

  The first variable current source 332 is connected between the first constant current source 322 and the power supply VDD, and the second variable current source 336 is connected between the second constant current source 326 and the ground voltage. . The first variable current source 332 receives a voltage V1 that is one of the differential voltages generated by the differential voltage generation circuit 310, and the second variable current source 336 receives the other differential voltage. A voltage V2 is input.

  The first variable current source 332 varies the current I3 to be output according to the input voltage V1. The second variable current source 336 has the same configuration as the first variable current source 332, and varies the output current I4 according to the input voltage V2. Since the voltage V1 and the voltage V2 input to the first variable current source 332 and the second variable current source 336 are differential voltages, the current I3 and the current I4 have a relationship of (I3 = −I4), They are out of phase with each other.

  A first output terminal 304 is connected to a current dividing point 312 between the first constant current source 322 and the first variable current source 332. Since the output current I1 of the first constant current source 322 is a constant current and the output current I3 of the first variable current source 332 is variable according to the voltage V1, the current output from the first output terminal 304 The CSN, that is, the difference current between the currents I1 and I3 is variable according to the current I3.

  A second output terminal 306 is connected to a current dividing point 316 between the second constant current source 326 and the second variable current source 336. Since the output current I2 of the second constant current source 326 is a constant current and the output current I4 of the second variable current source 336 is variable depending on the voltage V2, the current CSP output from the second output terminal 306, that is, The difference current between the currents I2 and I4 is variable according to the current I3.

  In the voltage controlled current source 100 shown in FIG. 1, the power supply VDD, the first constant current source 122, the first variable current source 132, and the ground voltage are connected in this order, but in the voltage controlled current source 300, The power supply VDD, the first variable current source 332, the first constant current source 322, and the ground voltage are connected in this order. Similarly, in the voltage controlled current source 100, the power supply VDD, the second constant current source 126, the second variable current source 136, and the ground voltage are connected in this order. The power supply VDD, the second variable current source 336, the second constant current source 326, and the ground voltage are connected in this order. The voltage controlled current source 300 having such a connection configuration can also perform the same function as the voltage controlled current source 100.

  The differential voltage generation circuit 310, the first constant current source 322, and the second constant current source 326 can be the same as the corresponding parts in the voltage controlled current source 100, and will be described in detail here. Omitted.

  Further, the first variable current source 332 and the second variable current source 336 have the same configuration except that the input voltages are in opposite phases to each other, so that only the first variable current source 332 is used here. Details will be described.

  FIG. 6 shows the configuration of the first variable current source 332. The first variable current source 332 converts the input voltage V1 into a current I3, and includes a P-type transistor P30, a first resistor R1, a second resistor R2, a third resistor R3, and an operational amplifier OP30. Is provided.

  The drain of the P-type transistor P30 is connected to the first constant current source 322 that provides the constant current I1, and the source is connected to one end of the first resistor R1. Note that the other end of the first resistor R1 is connected to the power supply VDD. The gate of the P-type transistor P30 is connected to the output of the operational amplifier OP30.

  The operational amplifier OP30 has an inverting terminal connected between the P-type transistor P30 and the first resistor R1, and a non-inverting terminal connected between the second resistor R2 and the third resistor R3 connected in series. The

  One end of the second resistor R2 is input with the voltage V1 from the differential voltage generating circuit 310, and the other end is connected to the third resistor R3.

  The third resistor R3 has one end connected to the second resistor R2 and the other end connected to the power supply VDD.

  A first output terminal 304 of the voltage controlled current source 300 is connected to a current dividing point 312 between the P-type transistor P30 and the first constant current source 322.

  A current flowing between the current dividing point 312 and the P-type transistor P30 is I3. As illustrated, the current CSN flowing from the current dividing point 312 to the first output terminal 304 is a difference current between the current I1 and the current I3. Since the current I1 is a constant current, the current CSN varies according to the current I3.

  The current I3 is controlled by the voltage input to the gate of the P-type transistor P30. This voltage is the output of the operational amplifier OP30.

  The voltage V1 input from the differential voltage generation circuit 310 to the first variable current source 332 is divided by the second resistor R2 and the third resistor R3, and “V1 × R3” is applied to the non-inverting terminal of the operational amplifier OP30. / (R2 + R3) "is input. That is, when the voltage V1 increases, the voltage input to the operational amplifier OP30 also increases, and the current I3 decreases accordingly.

  With such a configuration, the current I3 flowing through the P-type transistor P30 is controlled by the voltage V1.

  The same applies to the second variable current source 336, and the current I4 flowing therethrough is controlled by a voltage V2 having a phase opposite to that of the voltage V1.

  Since the voltages V1 and V2 input to the first variable current source 332 and the second variable current source 336 are differential voltages, the currents I3 and I4 are reverse-phase differential currents.

  Then, the current CSP and the current CSN, which are the outputs of the voltage controlled current source 300, are differential currents that vary according to the currents I3 and I4.

  The current CSP and the current CSN are controlled by the voltage V1 and the voltage V2 input to the first variable current source 332 and the second variable current source 336. The voltage V1 and the voltage V2 are generated from the input voltage Vin. Therefore, the output current CSP and the current CSN are controlled by the input voltage Vin.

  In this way, the voltage controlled current source 300 obtains the differential currents CSP and CSN from the input voltage Vin which is a single voltage signal, and can contribute to the suppression of power consumption in audio equipment and the like.

  The present invention has been described above based on the embodiment. The embodiment is an exemplification, and various changes and increases / decreases may be added without departing from the gist of the present invention. It will be understood by those skilled in the art that modifications to which these changes and increases / decreases are also within the scope of the present invention.

It is a schematic diagram of the voltage controlled current source concerning the 1st Embodiment of this invention. It is a figure which shows the detailed structure of the voltage control current source shown in FIG. It is a figure which shows the structure of the 1st variable current source in the voltage control current source shown in FIG. It is a figure which shows the structure of the voltage control current source concerning the 2nd Embodiment of this invention. It is a figure which shows the structure of the voltage control current source concerning the 3rd Embodiment of this invention. It is a figure which shows the structure of the 1st variable current source in the voltage control current source shown in FIG.

Explanation of symbols

  100 voltage controlled current source, 102 input terminal, 104 first output terminal, 106 second output terminal, 110 differential voltage generation circuit, 112 current dividing point, 116 current dividing point, 122 first constant current source, 126 Second constant current source, 132 First variable current source, 136 Second variable current source, 200 Voltage controlled current source, 202 Input terminal, 204 First output terminal, 206 Second output terminal, 212 Current division Point, 216 current dividing point, 242 circuit block, 246 circuit block, 300 voltage controlled current source, 302 input terminal, 304 first output terminal, 306 second output terminal, 310 differential voltage generating circuit, 312 current dividing point 316 current dividing point, 322 first constant current source, 326 second constant current source, 332 first Varying current source, 336 the second variable current source.

Claims (5)

A voltage-controlled current source that converts a voltage input from an input terminal into a differential current and outputs the differential current from the first output terminal and the second output terminal,
A differential voltage generation circuit that converts a voltage input from the input terminal into a differential voltage and outputs a first voltage and a second voltage;
A first constant current source connected between the first output terminal and a first power source;
A second constant current source connected between the second output terminal and the first power source;
A first output terminal is connected between the first output terminal and a second power source different from the first power source, and an output current is varied according to the first voltage input from the differential voltage generation circuit. 1 variable current source;
Connected between the second output terminal and the second power supply, has the same configuration as the first variable current source, and corresponds to the second voltage input from the differential voltage generation circuit And a second variable current source that varies the output current.
From the first output terminal, a difference current between the output currents of the first constant current source and the first variable current source is output,
A voltage-controlled current source that outputs a difference current between output currents of the second constant current source and the second variable current source from the second output terminal. The first variable current source includes a transistor and a first resistor connected in series between the first output terminal and the second power source,
An input terminal for inputting the first voltage from the differential voltage generation circuit;
A second resistor and a third resistor connected in series between the input terminal and the second power source;
An operational amplifier in which an inverting terminal is connected between the transistor and the first resistor, a non-inverting terminal is connected between the second resistor and a third resistor, and an output is connected to the gate of the transistor And
The second variable current source has the same configuration as the first variable current source, the transistor is connected to the second output terminal, and the input terminal is connected to the second variable current source from the differential voltage generation circuit. The voltage controlled current source according to claim 1, wherein two voltages are input. A first transistor and a second transistor constituting a differential pair;
A third constant current source connected between the first power source and the differential pair;
The differential voltage generation circuit inputs the first voltage and the second voltage to the gates of the first transistor and the second transistor, respectively.
The first variable current source includes:
A third transistor connected between the first output terminal and the second power supply;
A fourth transistor that is connected between the first transistor of the differential pair and the second power supply and that forms a current mirror with the third transistor;
The second variable current source is:
A fifth transistor connected between the second output terminal and the second power source;
2. The device according to claim 1, further comprising: a sixth transistor that is connected between the second transistor of the differential pair and the second power supply, and that forms a current mirror with the fifth transistor. Voltage controlled current source. The second power source is a ground voltage;
4. The voltage controlled current source according to claim 1, wherein transistors of the first variable current source and the second variable current source are N-type transistors. 5. The first power supply is a ground voltage;
4. The voltage controlled current source according to claim 1, wherein the transistors of the first variable current source and the second variable current source are P-type transistors. 5.

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