JP2001312321A - Constant current output circuit and square wave current generating circuit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant current output circuit capable of supplying the current of sharp rise and the current of high frequency, a square wave current generating circuit using the same and a triangular wave voltage generating circuit using this square wave current generating circuit. SOLUTION: One terminal of each of switches S1 and S2 is connected to an output point 4 of a current mirror circuit 1, the other terminal of the switch S1 is connected with the low potential side GND of a power source through a resistor R2, S2 is connected with an output terminal 3 of the constant current output circuit, a switch circuit 2 is composed of these switches S1, S2 and resistor R2 and S1 and S2 are operated with opposite phases. By turning on/off the switches S1 and S2, the current of sharp rise and an output current Iout 11 of high frequency are outputted from the output terminal 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant current output circuit to which a switch circuit for turning on / off a constant current circuit at high speed is added. Further, the present invention relates to a square wave current generation circuit using the same and a triangular wave voltage output circuit using the square wave current generation circuit.

[0002]

2. Description of the Related Art Power supplies, such as switching regulators, used in portable equipment, etc. are designed to be smaller and lighter.
The carrier frequency has been increased. Therefore, the constant current output circuit used in this power supply needs to turn on and off a constant DC voltage and current output from the constant current circuit at a high frequency. For this purpose, the constant current output circuit is provided with a switch circuit for turning on and off the voltage and current of the constant current circuit.

FIG. 9 shows an example of a conventional constant current output circuit.
This is a case where a p-channel MOSFET is used. The constant current output circuit includes a constant current circuit 51 including a current mirror circuit, and an output voltage / current of the constant current circuit 51 that is turned on / off.
The switch circuit 52 is turned off. This circuit is a source current output circuit using a p-channel MOSFET. Here, the description of the sink current output circuit constituted by the n-channel MOSFET is omitted.

A p-channel MOSF is connected to the high potential side Vdd of the power supply.
The source of M51 as ET and the source of M52 as p-channel MOSFET are connected, and the gate of M51 and M52 are connected.
And the gate of M51 is connected to the drain of M51. The drain of M51 is connected to one end of the resistor R51, and the other end is connected to the low potential side GND of the power supply. M52
Is connected to the output terminal 53 of the constant current circuit 51. This is a current mirror circuit. p-channel MOSF
The source of M53 as ET is connected to the high potential side Vdd of the power supply, and the drain of M53 is connected to the gate of M51.

In the constant current circuit 51, M51 and resistor R5
The reference current Iref51 flowing through 1 and the output current Iout51 output from the output terminal are equal. A signal D is applied to the gate terminal 54 of M53, and when the gate voltage (Vdd-gate potential), which is the voltage of this signal D, is smaller than the threshold voltage of M53, M53 is turned off. As a result, the source and the drain of M53 are short-circuited. M53
Is turned off, M51 and M52 are turned on, and Iout51 is output from the output terminal 53. On the other hand, when M53 is turned on, the gate voltages of M51 and M52 are reduced to the threshold voltage or less, M51 and M52 are turned off, and Iout53 output from the output terminal 53 is cut off. In this way, by turning M53 on and off, Iout51 output from the output terminal 53 is turned on and off.

[0006]

By the way, M53 is turned on, the source and drain of M53 are short-circuited, and M52 is turned on.
Takes a long time until the gate voltage becomes zero and M52 turns off. Of course, it takes time before M53 turns off and M52 turns on. The time delay (delay time) with respect to the signal D is such that when M53 is turned on, current flows from Vdd to the gates of M51 and M52, and charges are accumulated in the capacitances (gate capacitances) of the gate portions of M51 and M52. This is because it takes time for the voltage to rise. From another point of view, since the gate voltage of M52 changes (this means that the operating point of M52 moves), charges are taken in and out of the gate capacitance, which takes time. It can also be said. Due to this delay time, it is difficult for the conventional constant current output circuit to provide a current having a sharp rise and a high-frequency current.

As shown in FIG. 19, when a conventional constant current output circuit is formed as a square wave current generation circuit using a source current source 111 and a sink current source 112, a plus or minus value is required because of the delay time. It is difficult to provide an AC square wave current with a sharp rising current and a high-frequency current. The source current source 111 shown in FIG.
M51 is connected to the input terminal 73, and the reference current Iref51 is supplied from a reference current generation circuit (not shown). In addition, the sink current source 11
Similarly, for M2, M61 corresponding to M51 is connected to the input terminal 74. 71 is an output terminal, 72 is a gate terminal, Iref6
1 is the reference current, Iout61 is the output current of the sink current source,
out71 is a square wave output current, and M61, M62 and M63 are n
It is a channel MOSFET.

Further, as shown in FIG. 20, the same applies to the case where a triangular wave voltage output circuit is manufactured by connecting an oscillation capacitor to the output of the square wave generation circuit as shown in FIG. In the circuit shown in FIG. 20, an oscillation capacitor Cosc1 is connected to the outputs of two constant current output circuits, a source current source 113 and a sink current source 114, and the constant currents output from the source current source 113 and the sink current source 114 are used. It is generated by alternately repeating charging and discharging.
The output current Iout81 of the source current source 113 becomes the charging current of Cosc1, and the output current Iout82 of the sink current source 114 becomes the discharging current of Cosc1. To switch these currents, the source current source 113 and the sink current source 114 are alternately turned on and off.
Perform by turning off. Further, the on / off switching of the current source is performed by comparing a triangular wave voltage output with a voltage facilitated as a reference using a comparator. The voltages facilitated as the reference correspond to the reference voltages Vref1 and Vref2 in the figure. In some cases, two values of Vref1 and Vref2 are supplied from outside, or one of them is supplied and the other is generated inside the comparator. Here, temporarily, Vre
If f1> Vref2, the triangular wave voltage output shows a waveform of the minimum value Vref2 and the maximum value Vref1 as shown in the figure.

FIG. 21 shows another triangular wave voltage output circuit.
This circuit is composed of two constant current output circuits, a source power supply 115 and a sink power supply 116. The triangular wave voltage is
The difference between the output current Iout83 and the sink current Iout84 of the oscillation capacitor Cosc2 by the source current source 115 and the sink current source 116 becomes a charging current of the Cosc2, and the output current Iout4 of the sink current source 116 becomes a discharging current of the Cosc2.
Therefore, it is necessary to set these two currents so as to satisfy Iout83> Iout84 in order to generate a triangular wave. Switching of these currents is performed by turning on / off the source current source 115. The on / off switching of the current source is performed by comparing a triangular wave voltage output with a voltage prepared as a reference using a comparator.
The voltages prepared as the reference voltages correspond to Vref3 and Vref4 in the figure. In some cases, two values of Vref3 and Vref4 are supplied from outside, or one of them is supplied and the other is generated inside the comparator.
Here, if it is assumed that Vref3> Vref4, the triangular wave voltage output shows a waveform of the minimum value Vref4 and the maximum value Vref3 as shown in the figure.

FIG. 22 shows a conventional square wave generating circuit shown in FIG. The circuit of FIG. 22 turns on / off only the source current source 117 in the circuit of FIG.
3 is provided, and the sink current source is a constant current Iref51.
Keep flowing. The operation is similar to that of FIG. 9, when the gate voltage (VDD−gate potential) given by the signal to M53 is smaller than the threshold voltage of M53, M53 is turned off. The source and drain are short-circuited. By turning off M53, M51
And M52 are turned on, and Iref51-Iref is output from the output terminal 73.
61 is output. On the other hand, by turning on M53, M
The gate voltages of 51 and M52 are set to be equal to or lower than the threshold voltage,
M51 and M52 are turned off, and the sink current of Iref61 is output to the output terminal.

In the above-mentioned triangular wave voltage output circuit, it is difficult to supply a high-frequency square wave current having a sharp rise and fall due to a delay in the operation of the transistor. In short, excessive charging and discharging are performed for the delay time. For this reason, the amplitude becomes larger than the target triangular wave amplitude, and its influence becomes larger as the frequency becomes higher, and it becomes difficult to output a stable triangular wave voltage at a high frequency.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a constant current output circuit capable of supplying a steep rising current and a high-frequency current, and a steep rising current and a stabilizing current using the constant current generation output circuit. An object of the present invention is to provide an AC square wave current generating circuit capable of supplying a high-frequency current and a triangular wave voltage output circuit using the square wave current generating circuit.

[0013]

To achieve the above object, the following is provided. 1) In a constant current output circuit including a switch circuit and a constant current circuit, the switch circuit is added to an output point of the constant current circuit. 2) The switch circuit may be composed of two switches that operate in opposite phases. 3) The switch may be one of a MOS transistor and a bipolar transistor. 4) The constant current circuit is a current mirror circuit composed of an n-channel MOSFET, and the switch circuit comprises an n-channel MOSFET.
A source of the n-channel MOSFET and a drain of the p-channel MOSFET are both connected to an output point of a constant current circuit, and a source of the p-channel MOSFET is connected to a high potential of a power supply via a resistor. Side, the drain of the n-channel MOSFET is connected to the output terminal of the constant current output circuit, the gate of the n-channel MOSFET is connected to the gate of the p-channel MOSFET, and the gate is turned on and off. It is preferable that the output current of the constant current output circuit is turned on / off. 5) The constant current circuit is a current mirror circuit composed of a p-channel MOSFET, and the switch circuit
A n-channel MOSFET and a p-channel MOSFET.
The source of the channel MOSFET is connected to the output point of the constant current circuit, the source of the n-channel MOSFET is connected to the low potential side of the power supply via a resistor,
The drain of the OSFET is connected to the output terminal of a constant current output circuit, and the gate of the n-channel MOSFET is connected to the p-channel MOSFET.
It is preferable to connect the gate of the channel MOSFET and turn on / off the gate to turn on / off the output current of the constant current output circuit. 6) The p-channel MOSFET may be replaced with a pnp transistor, and the n-channel MOSFET may be replaced with an npn transistor. 7) The resistor may be a current mirror circuit composed of a MOSFET. 8) The constant current output circuit of the item 2) is a source current source and a sink current source, and is a square wave current generation circuit including the source current source and the sink current source. 9) A square wave current generation circuit including a constant current circuit including a switch circuit and a source current source and a constant current circuit including a sink current source, wherein the switch circuit is added to an output point of the source current source. Circuit. 10) It is assumed that the switch circuit of the item 9) is composed of two switches operating in opposite phases to each other. 11) The switch circuit according to the item 8), 9) and 10) is
One of an OS transistor and a bipolar transistor may be used. 12) The sink current source of item 8) is an n-channel MOS
A current mirror circuit comprising an FET, wherein the switch circuit comprises an n-channel MOSFET and a p-channel M
A current mirror circuit comprising an OSFET, wherein the source current source comprises a p-channel MOSFET,
The switch circuit is composed of a p-channel MOSFET and an n-channel MOSFET, and the gates of four MOSFETs constituting the switch circuit are connected, and the two current sources are alternately turned on by applying a rectangle to the gate. • Use a square-wave current generation circuit that turns off. 13) The constant current output circuit of item 4) is used as a source current source,
The constant current output circuit of 5) is used as a sink current source, and constitutes a current mirror circuit of the source current source. One reference current is withdrawn to form a current mirror circuit of the sink current source, and the n-channel MOSFET having a drain and a gate connected thereto.
A second reference current is supplied from a second reference current output stage circuit to the drain of T, and an output terminal of the source current source and an output terminal of the sink current source are connected at a first connection point.
A connection point is connected to an output terminal of a square-wave current generation circuit, and a gate of the p-channel MOSFET forming a switch circuit of the source current source and a gate of the n-channel MOSFET forming a switch circuit of the sink current source. Are connected at a second connection point, and the second connection point and a signal terminal of the square wave current generation circuit are connected to form a square wave current generation circuit. 14) The current mirror circuit of the source current source according to 13 above, wherein the drain of the p-channel MOSFET connected to the first reference current output stage circuit is not connected to the first reference current output circuit and the sink current is not connected. A square wave current circuit is connected to the drain of a new n-channel MOSFET constituting the current mirror circuit of the source, and is connected to the source of the n-channel MOSFET and the low potential side of the power supply. 15) The p-channel M of paragraphs 12), 13) and 14)
OSFET is a pnp transistor, the n-channel MO
The SFET may be replaced with an npn transistor. 16) The resistance described in 12), 13) and 14) is MO
It is assumed that the current mirror circuit is constituted by SFETs. 17) It is assumed that a load is connected between the output terminal of the square wave generating circuit described in the paragraphs 8) to 16) and the power source of the source side current source or the power source of the sink current source of the square wave generating circuit. 18) In a triangular wave voltage output circuit having a capacitor between an output terminal of a square wave current generating circuit including a source current source and a sink current source and a power source of the source current source or a power source of the sink current source, To 16) a triangular-wave voltage output circuit using the square-wave current generating circuit described in the item 16).

[0014]

FIG. 1 is a main part circuit diagram of a constant current output circuit according to a first embodiment of the present invention. In this circuit, the constant current circuit 1 is constituted by a p-channel MOSFET, and the switch circuit 2 is shown in a conceptual diagram. This constant current output circuit is a source current output circuit. The source of the p-channel MOSFET M1 and the source of the p-channel MOSFET M2 are connected to the high potential side Vdd of the power supply, the gate of M1 is connected to the gate of M2, and the gate of M1 is connected to the drain of M1. The drain of M1 is connected to one end of the resistor R1, and the other end is connected to the low potential side GND of the power supply. M2
To the output point 4 of the constant current circuit (this is a portion corresponding to the output terminal 53 in FIG. 9). This is the current mirror circuit 1. One end of each of the switches S1 and S2 is connected to the output point 4, and the other end of S1 is connected to the low potential side G of the power supply through a resistor R2.
Connect to ND. On the other hand, S2 is connected to the output terminal 3 of the constant current output circuit. The switch circuit 2 is constituted by S1, S2 and the resistor R2. The operation of S1 and S2 is characterized in that the operation is in the opposite phase that S2 is turned off when S1 is on and conversely S2 is turned on when S1 is off.

When S1 is turned off and S2 is turned on,
The output current Iout11 output from the output terminal 3 (this current is equal to the current Iout1 at the output point 4) is equal to the reference current Iref1 by the current mirror circuit. When S1 is turned on and S2 is turned off, Iout11 becomes zero. At this time, the gate voltage of M2 does not change, and M1 and M2 are always
Is in the ON state, the delay time is S1
And the delay time when S2 is turned on and off, and the influence of the gate capacitance of M1 and M2 is eliminated. Therefore, S1 and S2
By shortening the switching time from ON to OFF and from OFF to ON, a current having a sharp rise and a high-frequency output current Iout11 can be output from the output terminal 3.

FIG. 2 is a main part circuit diagram of a constant current output circuit according to a second embodiment of the present invention. In this circuit, the constant current circuit 5 is constituted by an n-channel MOSFET, and the switch circuit 6 is shown in a conceptual diagram. This circuit is a sink current output circuit. n-channel MOSFETs M3 and M
4. A constant current circuit 5 which is a current mirror circuit is constituted by the resistor R3, and a switch circuit 6 is constituted by the switches S3 and S4 and the resistor R4.
Is configured. Although the detailed circuit operation is omitted, the output point current Iout2 is equal to the reference current Iref2 by the current mirror circuit.

In this case, similarly to the first embodiment, S3 and S3
By shortening the switching time of the switch 4 from on to off and from off to on, a steep rising current and a high-frequency output current Iout21 can be output from the output terminal 7. Here, Iout21 is a return current from the load. FIG.
FIG. 9 is a main part circuit diagram of a constant current output circuit according to a third embodiment of the present invention. This circuit uses a constant current circuit 9 as a p-channel MOS
The case where the switching circuit 10 is constituted by a FET and the switching circuit 10 is constituted by a p-channel MOSFET, an n-channel MOSFET and a resistor is shown. This p-channel MOSFET is a pnp transistor, and the n-channel MOSFET is npn
It may be replaced with a transistor. The output point current Iout3 and the reference current Iref3 are substantially equal. This circuit is a source current output circuit.

In the circuit of FIG. 3, the switch corresponding to S1 in FIG. 1 is an n-channel MOSFET M7, and the switch corresponding to S2 is a p-channel MOSFET.
M8. By connecting the gates of M7 and M8 to each other, M7 and M8 can be operated in opposite phases. As described above, since M5 and M6 are always on (because there is no movement of the operating point), the steepness of the rise of the output current Iout31 of the constant current output circuit is M
7, determined by the switching time of M8. M7 and M8 are
In the ON state, the source and the drain are almost short-circuited, and the generated loss is small. Therefore, the occupied area can be smaller than that of M5 or M6 operating in the active state. Since the occupied area is reduced, the switching time of M7 and M8 is reduced, and output current I output from output terminal 11 is reduced.
The delay time of out31 with respect to the signal A input to the gate terminal 31 is reduced. Therefore, a current having a sharp rise and a high-frequency current can be output from the output terminal 11.

FIG. 4 is a main part circuit diagram of a constant current output circuit according to a fourth embodiment of the present invention. This circuit is a constant current circuit 13
Is constituted by an n-channel MOSFET, and the switch circuit 14 comprises a p-channel MOSFET and an n-channel MOSFET.
The case where it is composed of an OSFET and a resistor is shown. This p-channel MOSFET is connected to a pnp transistor and an n-channel M
The OSFET may be replaced with an npn transistor. The output point current Iout4 and the reference current Iref4 are substantially equal. This circuit is a sink current output circuit.

In the circuit of FIG. 4, the switch corresponding to S3 in FIG. 3 is a p-channel MOSFET M11, and the switch corresponding to S4 is an n-channel MOSFET.
M12. When the gates of M11 and M12 are connected to each other, they can operate in opposite phases. M
Since the source and the drain of M11 and M12 are almost short-circuited when turned on, the occupied area can be smaller than that of M9 and M10. As a result, the switching time is shortened, and the output current I
The delay time of out41 with respect to the signal B input to the gate terminal 41 is reduced. Therefore, a current having a sharp rise and a high-frequency current can be output from the output terminal 15. Here, Iout41 is a return current from the load.

FIG. 5 is a main part circuit diagram of a constant current output circuit according to a fifth embodiment of the present invention. In this case, the resistor R5 is replaced with a resistor equivalent circuit 41 configured by a combination of a current mirror circuit, and a load RL1 is connected between the output terminal 11 and the GND terminal 17. In this case, the same effect as above can be expected. FIG. 6 is an operation waveform diagram of the circuit of FIG. The upper part is the waveform of signal A, the middle part is the waveform of Iout31 in FIG. 5, and the lower part is the waveform of Iout51 of the conventional circuit. Since the delay time of the circuit of the present invention is shorter, the rise time of the current is shorter. Therefore, a current having a sharp rise and a high-frequency current can be supplied to the load as compared with the conventional circuit.

FIG. 7 is a main part circuit diagram of a constant current output circuit according to a sixth embodiment of the present invention. This is a case where the resistor R7 in FIG. 4 is replaced with a resistor equivalent circuit 42 constituted by a combination of a current mirror circuit, and a load RL2 is connected between the output terminal 15 and the Vdd terminal 18. In this case, the same effect as above can be expected. FIG. 8 is an operation waveform diagram of the circuit of FIG. The upper part shows the waveform of the signal B, the middle part shows the waveform of Iout41 in FIG. 7, and the lower part shows the waveform of the output current of the conventional circuit (sink current output circuit) not shown. Since the delay time of the circuit of the present invention is shorter, the rise time of the current is shorter. Therefore, a current having a sharp rise and a high-frequency current can be supplied to the load as compared with the conventional circuit.

FIG. 10 is a circuit diagram of a square wave current generating circuit according to a seventh embodiment of the present invention. This circuit includes a source current source 101 and a sink current source 102.
The source current source 101 is basically the same as the circuit of FIG. 1, and the sink current source 102 is basically the same as the circuit of FIG. Therefore, the same reference numerals are given to the same portions. In this circuit, M1 is connected to the input terminal 22 and M3
Are connected to the input terminal 23, and the output terminal 3 and the output terminal 7 are connected to the output terminal 21 to complete a square wave current generating circuit. The input terminals 22 and 23 are connected to a reference current generating circuit (not shown), and are supplied with reference currents Iref1 and Iref2. In this embodiment, Iref1 = Iou
Let t11 and Iref2 = Iout21.

The on / off switching of the source current source 101 is performed by two switches S1 and S2, and the operation is the same as that described with reference to FIG. The on / off switching of the sink current source 102 is performed by the two switches S3 and S4, and the operation is the same as that described in FIG. Of the four switches S1, S2, S3, S4,
As indicated by the arrows, S2 and S3 are turned on, and S1 and S3 are turned on.
By turning off 4, a source current of output current Iout 61 (= Iout 11) = Iref 1 is output from the output terminal 21. By turning off S2 and S3 and turning on S1 and S4, the output current Iout61 (= I
out21) = Iref2 sink current is output. Where I
ref1 and Iref2 are reference currents. By switching the output current paths of the current sources using the switches S1 and S4 and the switches S2 and S3, the operating points of the transistors M1 to M4 do not fluctuate, and the influence of the delay of the operation of these transistors can be avoided. Thus, by shortening the switching time of S1 to S4 from ON to OFF and from OFF to ON, a high-frequency square wave current having a sharp rise and fall (AC square wave current having positive and negative currents) is obtained. From the output terminal 21.

FIG. 11 is a circuit diagram of a square wave current generating circuit according to an eighth embodiment of the present invention. This circuit includes a source current source 103 and a sink current source 104.
The source current source 103 is basically the same as the circuit of FIG. 3, and the sink current source 104 is basically the same as the circuit of FIG. Therefore, the same reference numerals are given to the same portions. In this circuit, the switches corresponding to S1, S2, S3 and S4 in FIG.
8, M11 and M12. Source current source 10 in FIG.
The on / off switching operation of No. 3 is the same as that described with reference to FIG. The operation of switching on / off the sink current source 104 is the same as that described with reference to FIG.

The transistors M7 and M12 are n-channel M
OS8, M8 and M11 are p-channel MOS
The four transistors can be controlled by one signal (signal C in the figure) by using FETs, connecting the gates of these four transistors, and using them as input terminals. The effect of this circuit is the same as that described with reference to FIGS. 3 and 4, and a high-frequency square wave current having a sharp rise and fall can be output from the output terminal 24. In the drawing, Iout62 is an output current of the square wave current output circuit, and 42 is a gate terminal to which the signal C is input. 25 and 26 are input terminals, Iref3 and Iref4 are reference currents, and Iout31 and Iout41 are output currents of a source current source and a sink current source.

FIG. 12 is a circuit diagram of a square wave current generating circuit according to a ninth embodiment of the present invention. In this circuit, FIG.
The transistors M23 and M19 are used instead of the resistors corresponding to R3 and R4 in FIG. Also, I in FIG.
ref3 and Iref4 are equalized, and the reference currents Iref3, Ire
An input current Iin3 equal to f4 is input from the input terminal 28. That is, the circuit configuration is such that Iref3 = Iref4 = Iin3. Even with such a circuit configuration, it is possible to output a square wave current having a sharp rise and fall to the output terminal 27. Also, in this figure, the output terminal 27
, And a load capacitance CL1 is connected between the output terminal and the ground, and this output voltage can output a triangular wave voltage. With such a circuit configuration, as described later, the load capacitance CL
A triangular wave voltage, whose amplitude can be controlled even at a high frequency, can be output by a square wave current having a sharp rise and fall of the current flowing in 1.

When a resistor is connected to the output terminal as a load, the amplitude of the square wave current output from the square wave current generating circuit can be controlled. FIG.
FIG. 9 is a diagram showing operation waveforms of the second circuit. The upper part shows the waveform of the signal C supplied to the gate terminal 43, and the middle part shows Iout6 in FIG.
The lower waveform is the waveform of Iout71 of the conventional circuit. In the circuit of the present invention, the rise and fall times of the current are shorter because the delay time is shorter. For this reason,
As compared with the conventional circuit of FIG. 19 described above, a high-frequency square wave current having a sharp rise and a sharp fall can be supplied to the load.

FIG. 14 is a circuit diagram of a square wave current generating circuit according to a tenth embodiment of the present invention. This circuit includes a source current source 101 and a sink current source 102. The source current source 101 is basically the same as the circuit of FIG. 1, and the sink current source 102 is the same except that the switch circuit is not formed in the circuit of FIG.
Therefore, the same reference numerals are given to the same portions. In this circuit, M1 is connected to the input terminal 22, and M3 is connected to the input terminal 23.
And the output terminal 3 and the output terminal 7 are connected to the output terminal 29 to complete a square wave current generation circuit. The input terminals 22 and 23 are connected to a reference current generating circuit (not shown), and are supplied with reference currents Iref1 and Iref2. In this embodiment, Iref1> Iref2, Iref1 =
Iout11 and Iref2 = Iout21.

The on / off switching of the source current source 101 is performed by two switches S1 and S2, and the operation is the same as that described with reference to FIG. Two switches S
1, S2 is turned on as shown by the arrow among S2,
By turning off S1, the output current Iout64 (= Iout11-Iout21) = Iref1-Iref2 is output from the output terminal 29. Further, by turning off S2 and turning on S1, the output current Iout64 (= Iout21) is output from the output terminal 29.
= Iref2 is output. Where Iref1,
Iref2 is a reference current. By switching the output current path of the current source using the switches S1 and S2, the operating points of the transistors M1 to M4 do not change, and the influence of the delay in the operation of these transistors can be avoided. Thus, by shortening the switching time of S1 and S2 from on to off and from off to on, a high-frequency square wave current having a sharp rise and fall can be output from the output terminal 29.

FIG. 15 is a circuit diagram of a square wave current generating circuit according to an eleventh embodiment of the present invention. This circuit includes a source current source 103 and a sink current source 104. The source current source 103 is basically the same as the circuit of FIG. 3, and the sink current source 104 is the same as the circuit of FIG. 4 except that no switch circuit is formed.
Therefore, the same reference numerals are given to the same portions. In this circuit, the switches corresponding to S1 and S2 in FIG. 14 are the transistors M7 and M8. Source current source 103 in the figure
The operation of switching on / off is the same as that described with reference to FIG.

Transistor M7 is an n-channel MOSFE
T, M8 is composed of a p-channel MOSFET,
By connecting the gates of these two transistors and using them as input terminals, one transistor (signal C in the figure) can control the two transistors. The effect of this circuit is the same as that described with reference to FIG. 3, and a high-frequency square wave current having a sharp rise and fall can be output from the output terminal 30. In the figure, Iout65
Is an output current of the square wave current output circuit, and 42 is a gate terminal to which the signal C is input. 25 and 26 are input terminals, Iref3 and Iref4 are reference currents, and Iout31 and Iout41 are output currents of a source current source and a sink current source.

FIG. 16 is a circuit diagram of a square wave current generating circuit according to a twelfth embodiment of the present invention. In this circuit, instead of the resistor corresponding to R4 in FIG.
19 is used. Further, Iref3 and Iref4 in FIG. 15 are made equal, and an input current Iin4 equal to the reference currents Iref3 and Iref4 is input from the input terminal 32. That is, Iref3
= Iref4 = Iin4. In this case, the sizes of the transistors constituting the mirror circuit are adjusted so that Iout91> Iout92.

FIG. 17 is an operation waveform diagram using the triangular wave voltage output circuit of the thirteenth embodiment of the present invention. In the triangular wave voltage output circuit of FIG. 20, the circuit of FIG. 12 is used for the square wave current generating circuit. Is the case. As a comparative example, a case where the square wave current generating circuit of FIG. 19 is used is also shown. The first-stage waveform is the output voltage waveform of the present embodiment, the second-stage waveform is the output current waveform of the square-wave current generation circuit of the present embodiment,
The third stage waveform is a square wave current generating circuit as shown in FIG.
The output voltage waveform in the case of using the circuit of FIG. 19 is the output current waveform of the circuit of FIG.

Here, the oscillation capacitor Cosc1 has a value of 7.
The one with 5 pF was used. Since the delay time of the square wave current is shorter in the circuit of this embodiment than in the conventional example, the rise and fall times of the current are shorter, and a stable triangular wave voltage is secured. FIG. 18 is an operation waveform diagram using the triangular wave voltage circuit according to the fourteenth embodiment of the present invention.
This is a case where the circuit of FIG. 16 is used for the square wave current generation circuit in the triangular wave voltage output circuit of FIG. As a conventional example, a case where the square wave current generating circuit of FIG. 22 is used is also shown.

The first-stage waveform is the output voltage waveform of this embodiment,
The second stage waveform is the output current waveform of the square wave current generation circuit of the present embodiment, and the third stage waveform is the output voltage waveform when the conventional circuit of FIG. 22 is used as the square wave current generation circuit. Are the output current waveforms of the circuit of FIG. Here, an oscillation capacitor Cosc1 having a capacitance of 15 pF was used. Since the delay time of the square wave current is shorter in the circuit of this embodiment than in the conventional example, the rise and fall times of the current are shorter, and a stable triangular wave voltage is secured.

[0037]

According to the present invention, the MOS of the constant current circuit is provided.
The FET is always on, and two switches that operate in opposite phases are connected to the output terminal of the constant current circuit, so that the rise time (delay time) of the output current is shortened and the high-frequency pulse current is reduced. -A constant current output circuit that supplies a voltage to a load can be manufactured.

Further, by using this constant current output circuit as a source current source and a sink current source, the rising of the current,
It is possible to provide a square wave current generating circuit capable of supplying an AC high frequency square wave current having a sharp fall and a positive or negative current to a load. Further, in a triangular wave voltage output circuit using a capacitor as a load, by using this square wave current generating circuit, a rise and fall time of an output voltage can be reduced, and a high-speed triangular wave voltage can be output.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of a constant current output circuit according to a first embodiment of the present invention;

FIG. 2 is a main part circuit diagram of a constant current output circuit according to a second embodiment of the present invention;

FIG. 3 is a main part circuit diagram of a constant current output circuit according to a third embodiment of the present invention;

FIG. 4 is a main part circuit diagram of a constant current output circuit according to a fourth embodiment of the present invention;

FIG. 5 is a main part circuit diagram of a constant current output circuit according to a fifth embodiment of the present invention;

6 is an operation waveform diagram of the circuit of FIG.

FIG. 7 is a main part circuit diagram of a constant current output circuit according to a sixth embodiment of the present invention;

FIG. 8 is an operation waveform diagram of the circuit of FIG. 7;

FIG. 9 is a conventional constant current output circuit diagram.

FIG. 10 is a circuit diagram of a square wave current generating circuit according to a seventh embodiment of the present invention.

FIG. 11 is a circuit diagram of a square wave current generating circuit according to an eighth embodiment of the present invention.

FIG. 12 is a circuit diagram of a square-wave current generating circuit according to a ninth embodiment of the present invention.

FIG. 13 is a diagram showing operation waveforms of the circuit of FIG.

FIG. 14 is a circuit diagram of a square wave current generating circuit according to a tenth embodiment of the present invention.

FIG. 15 is a circuit diagram of a square wave current generating circuit according to an eleventh embodiment of the present invention.

FIG. 16 is a circuit diagram of a square wave current generating circuit according to a twelfth embodiment of the present invention.

FIG. 17 is an operation waveform diagram using a triangular wave voltage output circuit according to a thirteenth embodiment of the present invention.

FIG. 18 is an operation waveform diagram using a triangular wave voltage output circuit according to a fourteenth embodiment of the present invention.

FIG. 19 is a conventional square wave current generation circuit.

FIG. 20 shows an example of a triangular wave voltage output circuit.

FIG. 21 shows an example of a triangular wave voltage output circuit.

FIG. 22 shows a conventional square wave current generation circuit.

[Explanation of symbols]

1, 5, 9, 13 Constant current circuit 2, 6, 10, 14 Switch circuit 3, 7, 11, 15, 21, 24 Output terminal 27, 29, 30, 31 Output terminal 4, 8, 12, 16 Output point 17 GND terminal 18 Vdd terminal 22 to 26, 28 Input terminal 31, 41, 42, 43 Gate terminal S1, S2, S3, S4 Switch M1, M2, M5, M6, M8 p-channel MOSFE
T M11, M15, M16, M18 p-channel MOSF
ET M21, M23, M33, M34 p-channel MOSF
ET M3, M4, M7, M9, M10 n-channel MOSF
ET M12, M13, M14, M17 n-channel MOSF
ET M19, M20, M22 n-channel MOSFET M31, M32, M35, M36 n-channel MOSFET
ET Iref1, Iref2, Iref3, Iref4 Reference currents Iout1, Iout2, Iout3, Iout4 Output point currents Iout11, Iout21, Iout31, Iout41 Output currents Iout61, Iout62, Iout63 Output currents Iout64, Iout65, Iout66 Input currents Iin1, Iin1, Iin1

Claims (18)

[Claims] 1. A constant current output circuit comprising a switch circuit and a constant current circuit, wherein the switch circuit is added to an output point of the constant current circuit. 2. The constant current output circuit according to claim 1, wherein said switch circuit comprises two switches operating in opposite phases. 3. The constant current output circuit according to claim 2, wherein said switch circuit is one of a MOS transistor and a bipolar transistor. 4. The constant current circuit is an n-channel MOSFET.
Wherein the switch circuit comprises an n-channel MOSFET and a p-channel MOSFET.
T, the source of the n-channel MOSFET and the drain of the p-channel MOSFET are both connected to the output point of the constant current circuit,
Is connected to the high potential side of the power supply via a resistor, the drain of the n-channel MOSFET is connected to the output terminal of the constant current output circuit, and the gate of the n-channel MOSFET is connected to the gate of the p-channel MOSFET. And
2. The constant current output circuit according to claim 1, wherein an output current of the constant current output circuit is turned on / off by turning on / off the gate. 5. The method according to claim 1, wherein the constant current circuit is a p-channel MOSFET.
Wherein the switch circuit comprises an n-channel MOSFET and a p-channel MOSFET.
T, the drain of the n-channel MOSFET and the source of the p-channel MOSFET are both connected to the output point of the constant current circuit, the source of the n-channel MOSFET is connected to the low potential side of the power supply via a resistor, The drain of the p-channel MOSFET is connected to the output terminal of the constant current output circuit, the gate of the n-channel MOSFET is connected to the gate of the p-channel MOSFET, and the gate is turned on / off, thereby providing a constant current output circuit. 2. The constant current output circuit according to claim 1, wherein the output current is turned on / off. 6. The semiconductor device according to claim 4, wherein said p-channel MOSFET is replaced with a pnp transistor, and said n-channel MOSFET is replaced with an npn transistor.
2. The constant current output circuit according to 1. 7. The current mirror circuit according to claim 4, wherein said resistor is a current mirror circuit composed of a MOSFET.
2. The constant current output circuit according to 1. 8. A constant current output circuit according to claim 2, wherein the source current source and the sink current source are used, an output point of the source current source is connected to an output point of the sink current source, and an output terminal is connected to the connected point. A square-wave current generating circuit comprising: 9. A square wave current generating circuit comprising a constant current circuit comprising a switch circuit and a source current source and a constant current circuit comprising a sink current source, wherein an output point of the source current source and an output point of the sink current source are provided. A square wave current generating circuit, comprising: an output terminal at the connected point; and the switch circuit being added to an output point of a source current source. 10. The square-wave current generating circuit according to claim 9, wherein said switch circuit comprises two switches operating in opposite phases. 11. The square wave current generating circuit according to claim 8, wherein said switch circuit is one of a MOS transistor and a bipolar transistor. 12. The sink current source is an n-channel MOS.
A current mirror circuit comprising an FET, wherein the switch circuit comprises an n-channel MOSFET and a p-channel M
A current mirror circuit comprising an OSFET, wherein the source current source comprises a p-channel MOSFET,
The switch circuit is composed of a p-channel MOSFET and an n-channel MOSFET, and the two current sources are turned on alternately by connecting the gates of four MOSFETs constituting the switch circuit and applying a rectangular wave to the gate. The square-wave current generation circuit according to claim 8, wherein the circuit is turned off. 13. A constant current output circuit according to claim 4 as a source current source, a constant current output circuit according to claim 5 as a sink current source, and a current mirror circuit of said source current source, wherein a drain and a gate are connected. Said p-channel MOSFET
A first reference current is extracted from the drain of the n-channel MOSFET by a first reference current output stage circuit to form a current mirror circuit of the sink current source. A second reference current is supplied from an output stage circuit, and an output terminal of the source current source and an output terminal of the sink current source are connected at a first connection point, and the first connection point is connected to an output of a square wave current generation circuit. And a gate of the p-channel MOSFET forming a switch circuit of the source current source and an n-channel MOSF forming a switch circuit of the sink current source.
A square wave current generating circuit, wherein a gate of the ET is connected at a second connection point, and the second connection point is connected to a signal terminal of the square wave current generation circuit. 14. A current mirror circuit for the source current source, wherein a drain of the p-channel MOSFET connected to the first reference current output stage circuit is not connected to the first reference current output stage circuit and the sink current is not connected. 14. The square wave current generator according to claim 13, wherein the source is connected to a drain of a new n-channel MOSFET constituting the current mirror circuit, and is connected to a source of the n-channel MOSFET and a low potential side of a power supply. circuit. 15. The square-wave current generating circuit according to claim 12, wherein said p-channel MOSFET is replaced by a pnp transistor, and said n-channel MOSFET is replaced by an npn transistor. 16. The square wave current generating circuit according to claim 13, wherein said resistor is a current mirror circuit formed of a MOSFET. 17. A square wave current generating circuit according to claim 8, wherein a load is connected between said output terminal and a power source of a source current source or a power source of a sink current source. A square-wave current generating circuit. 18. A triangular wave voltage output circuit comprising a capacitor between an output terminal of a square wave current generating circuit comprising a source current source and a sink current source and a power source of a source current source or a power source of a sink current source. A triangular wave voltage output circuit using the square wave current generating circuit according to claim 8.