JPH06291576A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To realize an arbitrary frequency characteristic. CONSTITUTION:A constant current source transistor 11a is constituted of plural transistors whose size is the same or different which can be operated after the arbitrary number of the transistors can be selected by a control signal from a first selecting register 8a. Also, a phase compensating capacitor is constituted of the plural capacitors whose capacity is the same or different which can be operated after the arbitrary number of the transistors can be selected by the control signal from a second selecting register.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit in which a CMOS operational amplifier circuit is incorporated and frequency characteristics can be changed.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a semiconductor integrated circuit incorporating a conventional CMOS operational amplifier circuit. In the figure, 1 is a normal input of an operational amplifier, 2 is an inverting input of an operational amplifier, 3 is an operational amplifier output, and 9 is an operational amplifier output. Is the current mirror circuit,
10 is an MO composed of an inverting input 2 and a non-inverting input 1
An S differential amplifier pair 11 is a constant current source transistor. Further, 5 is a differential amplifier circuit composed of the current mirror circuit 9, the MOS differential amplifier pair 10 and the constant current source transistor 11, and 6 is an M for further amplifying the output of the differential amplifier circuit 5.
It is an OS inverter type output buffer. Further, 7 is a phase compensation capacitor connected between the differential amplifier circuit 5 and the MOS inverter type output buffer 6, 4 is a constant voltage source, the gate input of the constant current source transistor 11, and M
It is connected to the Nch gate input of the OS inverter type output buffer 6.

Next, the operation will be described. This CMOS
The operational amplifier circuit is a normal input 1 of the MOS differential amplifier pair 10.
The potential difference between the inverting input 2 and the inverting input 2 is amplified by the differential amplifier circuit 5, further amplified by the MOS inverter type output buffer 6, and output from the operational amplifier output 3. That is, when the gate voltage applied to the non-inverting input 1 and the inverting gate 2 are equal, the current flowing in the constant current source transistor is I, the current flowing in the MOS differential amplifier pair is I ₁ = I ₂ = I / 2. . Now, from the state where the gate voltages applied to the normal input 1 and the inverting input 2 are balanced, the level of the inverting input 2 is ΔV.
A change of only ₁ causes a current change of I ₁ → I ₁ + ΔI. On the other hand, since the current I ₂ is I ₂ + I ₁ = I (constant), the current I ₂ changes by I ₂ −ΔI. Due to this change in the current I ₂ , the output voltage Vx of the differential amplifier circuit 5
Changes Vx + ΔVx. The amplification factor of the differential amplifier circuit is a change in output ΔVx / ΔV with respect to a change in input, and they depend on the current I. Therefore, if the current I is changed by changing the size of the constant current source transistor 11, ΔVx / ΔVx / ΔVx / ΔV ΔV also changes. The ratio of the change in the operational amplifier output 3 with respect to the change in the potential difference between the normal input 1 and the inverting input 2 is called an amplification factor. This amplification factor decreases as the frequency of the potential difference between the normal input 1 and the inverting input 2 increases. The characteristics (hereinafter referred to as frequency characteristics) are shown. This frequency characteristic is CM
It is determined by the current Ids flowing through the constant current source transistor 11 and the capacity of the phase compensation capacitor 7 in the OS operational amplifier circuit. In the conventional CMOS operational amplifier circuit, the current Ids and the capacity of the phase compensation capacitor are constant. Characterized.

[0004]

Since the conventional semiconductor integrated circuit is constructed as described above, the current flowing through the constant current source transistor 11 and the capacity of the phase compensating capacitor 7 are constant. There was a problem that it was impossible to realize the characteristics.

The invention of claim 1 has been made to solve the above-mentioned problems, and an arbitrary number of transistors in the constant current source transistor are selectively operated to make it possible to operate as desired. An object is to obtain a semiconductor integrated circuit that can realize frequency characteristics.

An object of the present invention is to obtain a semiconductor integrated circuit capable of realizing desired arbitrary frequency characteristics by selectively operating an arbitrary number of capacitors among the phase compensation capacitors. .

According to the third aspect of the present invention, a further fine frequency characteristic can be realized by selectively operating the arbitrary number of transistors in the constant current source transistor and the arbitrary number of capacitors in the phase compensation capacitor. The purpose is to obtain a semiconductor integrated circuit.

[0008]

According to another aspect of the semiconductor integrated circuit of the present invention, a constant current source transistor can be operated by selecting an arbitrary number of constant current source transistors by a control signal from a first selection register. It is composed of a plurality of transistors of different sizes or different sizes.

A semiconductor integrated circuit according to a second aspect of the invention is
The phase compensating capacitor is composed of a plurality of capacitors having the same capacity or different capacities that can be operated by selecting an arbitrary number of them by a control signal from the second selection register.

A semiconductor integrated circuit according to the invention of claim 3 is
The constant current source transistor is composed of a plurality of transistors of the same size or different sizes that can be operated by selecting an arbitrary number of transistors according to the control signal from the selection register, and the phase compensation capacitor is connected from the second selection register. It is composed of a plurality of capacitors having the same capacity or different capacities that can be selected and operated by any number of control signals.

[0011]

According to the semiconductor integrated circuit of the present invention, the constant current source transistors are selected according to the number of transistors which are selected and operate, or different sizes are selected. The frequency characteristic according to the magnitude of the flowing current is obtained.

In the semiconductor integrated circuit according to the second aspect of the present invention, a predetermined frequency characteristic is obtained by selecting each of the capacitors forming the phase compensating capacitor and operating the capacitors, or by selecting capacitors having different capacities. .

In the semiconductor integrated circuit according to the third aspect of the present invention, the number of operating transistors constituting the constant current source transistor and the number of operating phase compensating capacitors can be arbitrarily selected, so that the frequency can be more accurately measured. Allows the property to be set.

[0014]

EXAMPLES Example 1. Hereinafter, an embodiment of the invention of claim 1 will be described with reference to the drawings. In FIG. 1, 1 is a non-inverting input of an operational amplifier, 2 is an inverting input of an operational amplifier, 3 is an operational amplifier output, 9 is a current mirror circuit, 10 is a MOS differential amplifier pair composed of an inverting input 2 and a non-inverting input 1, 11a
Is a constant current source transistor including a plurality of transistors each having the same or different size. Further, 5 is a differential amplifier circuit composed of the current mirror circuit 9, the MOS differential amplifier pair 10 and the constant current source transistor 11a,
6 is a MOS inverter type output buffer for further amplifying the output of the differential amplifier circuit 5, and 7 is the differential amplifier circuit 5 and MO
It is a phase compensation capacitor connected to the S inverter type output buffer 6. Further, 4 is a constant voltage source, which is a gate input of each constant current source transistor 11a and a MOS.
It is connected to the Nch gate input of the inverter type output buffer 6. 8a is a plurality of constant current source transistors 11
It is a first selection register for selecting an arbitrary number of transistors of the same size or different sizes from a.

Next, the operation will be described. In this CMOS operational amplifier circuit, the potential difference between the non-inverting input 1 and the inverting input 2 of the MOS differential amplifier pair 10 is amplified by the differential amplifier circuit 5, further amplified by the MOS inverter type output buffer 6, and output from the operational amplifier output 3. To do. Forward input 1 and reverse input 2
The amplification factor, which is the ratio of the change in the operational amplifier output 3 with respect to the change in the potential difference of 1, exhibits a characteristic (hereinafter, referred to as a frequency characteristic) that decreases as the frequency of the potential difference between the non-inverting input 1 and the inverting input 2 increases. This frequency characteristic is determined by the current Ids flowing in the constant current source transistor 11a and the capacitance of the phase compensation capacitor 7 of the CMOS operational amplifier circuit.

In the present invention, the first selection register 8a selects any one of the plurality of constant current source transistors 11a, and the voltage from the constant voltage source 4 is fixed to the gate of the selected transistor. Apply voltage. The size of the selected transistor is different as described above, and a different current Ids is obtained depending on which is selected. That is, it is possible to obtain an arbitrary frequency characteristic by preparing a transistor of a required size as the constant current source transistor 11a and selecting an arbitrary transistor. Further, even with transistors of the same size, it is possible to obtain an arbitrary frequency characteristic by selecting these numbers.

Example 2. FIG. 2 is a circuit diagram showing a semiconductor integrated circuit according to an embodiment of the present invention. In FIG. 2, 1 is a normal input of an operational amplifier, 2 is an inverting input of an operational amplifier, 3 is an operational amplifier output, and 9 is a current mirror. circuit,
10 is an MO composed of an inverting input 2 and a non-inverting input 1
An S differential amplifier pair 11 is a constant current source transistor. 5
Is a differential amplifier circuit composed of a current mirror circuit 9, a MOS differential amplifier pair 10, and a constant current source transistor 11, 6
Is a MOS inverter type output buffer for further amplifying the output of the differential amplifier circuit 5. Further, 7a is a phase compensation capacitor in which a plurality of capacitors having arbitrary capacitances connected between the differential amplifier circuit 5 and the MOS inverter type output buffer 6 are connected in parallel, 4 is a constant voltage source, and a constant current source transistor 11 , And the Nch gate input of the MOS inverter type output buffer 6. 8b
Is a second selection register for selecting an arbitrary number of capacitors having the same or different capacities from the phase compensation capacitors 7a.

According to this embodiment, an arbitrary frequency characteristic can be obtained by selecting an arbitrary capacitor from the phase compensating capacitors 7a by the selection register 8b.

Example 3. In each of the above embodiments, the frequency characteristic is selected by selecting either the transistor or the capacitor, but the phase compensation capacitor 7a having a plurality of capacitors and the constant current source having a plurality of transistors are shown. A finer frequency characteristic can be selected by providing the transistor 11a, the phase compensation capacitor selection register 8b, and the constant current source transistor selection register 8a, and selecting an arbitrary number of capacitors and transistors, respectively.

[0020]

As described above, according to the first aspect of the present invention, the constant current source transistors of the same size or selected by the control signal from the first selection register can be operated in any number. Since it is composed of a plurality of transistors of different sizes, there is an effect that a desired frequency characteristic can be arbitrarily and easily set.

According to the second aspect of the invention, a plurality of phase compensating capacitors having the same capacitance or different capacitances which can be selected and operated by a control signal from the second selection register are operable. Since it is composed of capacitors, there is an effect that a required frequency characteristic can be set arbitrarily and easily by only selecting the number of the capacitors.

Further, according to the invention of claim 3, the constant current source transistor is composed of a plurality of transistors of the same size or different sizes which are selected and operated by a control signal from the selection register. Then
Moreover, since the phase compensating capacitor is composed of a plurality of capacitors having the same capacity or different capacities that can be operated by selecting an arbitrary number by the control signal from the second selection register, the frequency characteristics can be further divided. There is an effect that one that can arbitrarily and easily set one of these can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a semiconductor integrated circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a semiconductor integrated circuit according to an embodiment of the invention of claim 2;

FIG. 3 is a circuit diagram showing a conventional semiconductor integrated circuit.

[Explanation of symbols]

 5 differential amplifier circuit 6 MOS inverter type output buffer 7, 7a phase compensation capacitor 8a first selection register 8b second selection register 9 current mirror circuit 10 MOS differential amplification pair 11, 11a constant current source transistor

Claims (3)

[Claims] 1. A differential amplifier circuit comprising a current mirror circuit, a MOS differential amplifier pair and a constant current source transistor,
In the semiconductor integrated circuit including a MOS inverter type output buffer for amplifying the output of the differential amplifier circuit and a phase compensation capacitor connected between the MOS inverter type output buffer and the differential amplifier circuit, the constant current 2. A semiconductor integrated circuit, characterized in that the source transistor is composed of a plurality of transistors of the same size or different sizes, which can be operated by selecting an arbitrary number of them by a control signal from the first selection register. 2. A differential amplifier circuit comprising a current mirror circuit, a MOS differential amplifier pair, and a constant current source transistor,
In the semiconductor integrated circuit including a MOS inverter type output buffer for amplifying the output of the differential amplifier circuit and a phase compensation capacitor connected between the MOS inverter type output buffer and the differential amplifier circuit, the phase compensation The semiconductor integrated circuit is characterized in that the capacitors for use are composed of a plurality of capacitors having the same capacity or different capacities that can be operated by selecting an arbitrary number of capacitors by a control signal from the second selection register. 3. A differential amplifier circuit comprising a current mirror circuit, a MOS differential amplifier pair and a constant current source transistor,
In the semiconductor integrated circuit including a MOS inverter type output buffer for amplifying the output of the differential amplifier circuit and a phase compensation capacitor connected between the MOS inverter type output buffer and the differential amplifier circuit, the constant current The source transistor is composed of a plurality of transistors of the same size or different sizes that can be operated by selecting an arbitrary number of them by the control signal from the first selection register, and the phase compensation capacitor is set to the second selection. A semiconductor integrated circuit comprising a plurality of capacitors having the same capacity or different capacities which can be selected and operated by a control signal from a register.