JP3141892B2 - Operational amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operational amplifier for amplifying and outputting a difference between voltages applied to an inverting input terminal and a non-inverting input terminal, and more particularly to an operational amplifier realizing a wide common-mode input voltage range. is there.

[0002]

2. Description of the Related Art As an operational amplifier, as shown in FIG.
Inverting input terminal 1, the first to the non-inverting input terminal 2, a second differential input circuits 3 and 4 are connected in common, their differential input circuit 3,
In some cases, the output of the output circuit 4 is independently provided to the output circuit 5. 6 is an output terminal.

The first differential input circuit 3 has a differential connection NP
It comprises N-transistors Q1 and Q2, PNP transistors Q3 and Q4 connected as a current mirror as active loads, and a constant current source 7. The second differential input circuit 4 includes PNP transistors Q5 and Q6 of a differential connection, an NPN transistor Q7 of a current mirror connection as an active load,
Q8 and a constant current source 8. Further, the output circuit 5
PNP transistors Q9-Q11, NPN transistors Q12-Q14, capacitors C1-C4, resistors R1-R
4

When the voltage V1 at the inverting input terminal 1 and the voltage V2 at the non-inverting input terminal 2 satisfy V1 <V2, the transistor Q9 is turned on by the first differential input circuit 3.
Of the transistor Q12 is also lowered by the second differential input circuit 4. As a result, the voltage Vo at the output terminal 6 increases. Conversely, V1
> V2, the transistor Q9, the transistor Q1
2, the base potential of the output terminal 6 increases, and conversely, the voltage Vo of the output terminal 6 decreases.

[0005]

[SUMMARY OF THE INVENTION However, in this circuit, between the power supply + V _CC and -V _EE, constant current source connected in series therewith the transistors Q1, Q2, Q5, Q6 of a differential input circuit 7, 8 and the current mirror connection transistors Q3, Q4, Q7, Q8 are interposed, so that the common mode input range is narrowed.

For example, on the side of the inverting input terminal 1, the collector-emitter saturation voltage V _CE (Ｖ0.
3v) can only be input up to a voltage higher than -V _EE ,
Further, the voltage V _CE of the transistor Q3 connected to the current mirror is connected _.
Not only it can enter up to a voltage lower than the only + V _CC minute minute. On the other hand, the transistor Q
8. The input voltage range is limited at Q3. in this way,
Absorption voltage due to transistor saturation voltage V _CE is + V
_CC side, since generated at -V _EE side, the input voltage range is narrowed.

The output of the first differential input circuit 3 and the second
Since the outputs of the differential input circuit 4 are separately input to the output circuit 5, it is difficult to stably compensate the phase even if the capacitors C1 to C4 are used, and it is also difficult to widen the frequency band. SUMMARY OF THE INVENTION An object of the present invention is to provide an operational amplifier having a wide common mode input range and capable of stabilizing phase compensation.

[0008]

An operational amplifier according to the present invention comprises:
The base is connected to the inverting input terminal and the collector is connected to the second power supply.
A first transistor having a first polarity directly connected to the first transistor;
First pole connected to Darlington to emitter of transistor
Second transistor, base connected to non-inverting input terminal
A first polarity in which a collector is directly connected to the second power supply
Of the third transistor, the emitter of the third transistor
A fourth transistor of a first polarity connected in Darlington,
A common connection emitter of the second and fourth transistors and a first
A first input circuit comprising a first current source connected to a power supply
And a base connected to the inverting input terminal and the first
A collector opposite to said first polarity, wherein the collector is directly connected to the source;
Fifth bipolar transistor, base connected to the non-inverting input terminal
And the collector is directly connected to the first power supply.
A sixth transistor having a second polarity,
Diode of first polarity with emitter connected to emitter
Connection of the seventh transistor and the sixth transistor
Diode connection of the first polarity, whose emitter is connected to the
An eighth transistor, an emitter of the fifth transistor
A ninth transistor of the first polarity, the emitter of which is connected to
An emitter is connected to an emitter of the sixth transistor.
A tenth transistor having a first polarity, and the seventh and eighth transistors
Connected between the common connection base of the transistor and the second power supply.
A second input circuit comprising a second current source (14)
A collector output of the second transistor of the first input circuit;
The collector of the tenth transistor of the second input circuit
The outputs are added on the reference side, and the fourth trigger of the first input circuit is added.
A collector output of the transistor and the second input circuit;
Curry that adds the collector output of 9 transistors on the output side
And the output of the current mirror circuit.
And an output circuit connected to receive the force.
Was configured.

[0009]

According to the present invention, since the collectors of the input transistors of the first and second input circuits are directly connected to the power supply,
The common mode input voltage range extends to its power supply voltage. Then, the outputs of the first and second input circuits are added by a current mirror circuit. Here, the outputs can be combined into one common signal and sent to the output circuit. Phase compensation is performed.

[0010]

Embodiments of the present invention will be described below. FIG. 1 is a circuit diagram of an operational amplifier according to one embodiment. Reference numeral 11 denotes a first input circuit, which is a pair of transistors Q21, Q22, and Darlington-connected to the inverting input terminal 1.
Similarly, it comprises a pair of transistors Q23 and Q24 connected to the non-inverting input terminal 2 in Darlington, and a constant current source 12 connected to the emitter of each set of Darlington-connected transistors Q22 and Q24 and the power supply + _VCC line. .

A second input circuit 13 includes a transistor Q25 having a base connected to the inverting input terminal 1, a transistor Q26 having a base connected to the non-inverting input terminal 2,
A transistor Q27 having an emitter commonly connected to the transistor Q25, a transistor Q28 having an emitter connected to the emitter of the transistor Q26, a transistor Q2
7 and a transistor Q whose base and emitter are connected in common
29, a transistor Q30 having a base and an emitter commonly connected to the transistor 28, transistors Q29 and Q3
It consists of a constant current source 14 connected between the 0 base collector and the power supply- _VEE line. The above transistor Q27
Q30 to Q30 are grounded bases, and convert the output of the second input circuit 13 (emitter output of the transistors Q25 and Q26) to the collector output of the transistors Q27 and Q28. Transistors Q29 and Q30 are transistors Q
These transistors are connected so as to supply a sufficient emitter current to Q25 and Q26.

Reference numeral 15 denotes a current mirror circuit including transistors Q31 and Q32.
2 and Q24 and as active loads of both transistors 27 and Q28. That is, the output of the first input circuit 11 and the output of the second input circuit 13 are
In-phase addition is performed at 5. And this current mirror circuit 1
5 outputs one output. R5 and R6 are resistors.

A normal output circuit 16 receives the output of the current mirror 15, and includes transistors Q33 to Q33.
35, constant current sources 17 and 18, phase compensation capacitor C
5, consisting of a resistor R7.

In the operational amplifier of this embodiment, if the voltage V1 at the inverting input terminal 1 satisfies V1 <V2 with respect to the voltage V2 at the non-inverting input terminal 2, the collector of the transistor Q22 in the first input circuit 11 When the current becomes larger than that of the transistor Q24, the transistor Q31
Of the transistor Q32
Current required for the collector of transistor Q33 increases, and the current is supplied as the emitter current of transistor Q33.
The emitter current increases, the emitter current of the transistor Q34 and the collector current of the transistor Q35 decrease, and the output voltage Vo of the output terminal 6 increases.

At this time, in the second input circuit 13,
The transistor Q is more than the emitter current of the transistor 25.
26, so that transistor Q28
Of the transistor Q27 becomes larger than that of the transistor Q27, resulting in a further increase in the collector current of the transistor Q31. Therefore, the output terminal 6 is also made higher by the second input circuit 13.

As described above, when the input voltage is V1> V2, the first input circuit 11 and the second input circuit 13 work simultaneously, and their outputs are added by the current mirror circuit 15,
The voltage Vo at the output terminal 6 is increased.

Conversely, if the input voltage becomes V1> V2, the first and second input circuits 11 and 13 work in the opposite manner to add their outputs in the current mirror circuit 15 and the output terminal 6 Voltage Vo decreases.

By the way, in the operational amplifier of this embodiment,
For example, when the voltage of the inverting input terminal 1 approaches the -V _EE side, at a certain time (the sum of the total base-emitter voltage 2V _{BE of the} transistors Q25 and Q29 and the collector-emitter saturation voltage V _CE of the transistor constituting the constant current source 14) At the time when a voltage difference smaller than the value is left), the transistors Q25, Q27, and Q29 are completely cut off. However, the base current to the transistor Q21, Q22 acts by the current mirror circuit 15 so Koretaku current flows, even if reduced to the power supply voltage even the inverting input terminal 1 -V _EE same potential, continued entire circuit operation I do. The same applies to the non-inverting input terminal 2 side.

Further, the inverted output terminal 1 approaches + V _CC side, the sum of a point in time (transistors Q21, Q22 total base-emitter voltage 2V _BE and collector-emitter saturation voltage V _CE of the transistor to be 12 constituting a constant current source At the time when a voltage difference of less than is left, the transistors Q21 and Q22 are completely cut off. However, since the base current flows through the transistor Q25, acts by the current mirror circuit 15 the collector current flows through the transistor Q27, also increased to an inverting input terminal 1 is for example the power supply voltage + V _CC and the same potential, the entire circuit Continues operation. The same applies to the non-inverting input terminal 2 side.

As described above, in the operational amplifier of this embodiment,
The input voltage applied to input terminals 1 and 2 is + V _{CC of the} power supply voltage
It operates normally up to a voltage in the range of _-VEE . That is, the in-phase input range is widened.

The first input circuit 11 and the second input circuit 1
Since the three collectors are added in phase in the current mirror circuit 15, the output can be made single-ended, and the output circuit 16 having a normal circuit configuration can be used, and the phase compensation can be stably realized. .

In the above embodiment, the constant current source 1
2, 14, 17, and 18 can be replaced with resistors. Further, the same configuration can be adopted by exchanging the PNP transistor and the NPN transistor, and reversing the power supply + V _CC and −V _EE .

As described above, according to the present invention, since the input voltage can be applied to the entire power supply voltage range and normal operation can be performed, the common-mode input range can be greatly expanded. In addition, since the output of the input circuit is single-ended, a normal output circuit can be used for the output circuit, whereby phase compensation can be stably performed without reducing the bandwidth.
There is an advantage that an operational amplifier that operates stably can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an operational amplifier according to one embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional operational amplifier.

[Explanation of symbols]

1: inverting input terminal, 2: non-inverting input terminal, 6: output terminal, 11: first input circuit, 12: constant current circuit, 13: second input circuit, 14: constant current circuit, 15: current mirror circuit, 16: output circuit.

Claims (1)

(57) [Claims] A second power supply having a base connected to the inverting input terminal;
Transistor of the first polarity, the collector of which is directly connected to the first transistor
Darlington connection to the emitter of the first transistor
To the second transistor of the first polarity,
The base is connected and the collector is directly connected to the second power supply.
A third transistor of a first polarity, the third transistor being
The fourth transistor of the first polarity connected to the Darlington
Transistor, the common connection of the second and fourth transistors.
From a first current source connected between the
A first input circuit, and a base connected to the inverting input terminal and connected to the first power supply.
A second polarity opposite to the first polarity to which the collector is directly connected
The fifth transistor has a base connected to the non-inverting input terminal.
A second pole connected to the first power supply and having a collector connected directly to the first power supply
Of the sixth transistor and the fifth transistor
Diode of the first polarity, whose emitter is connected to the
A seventh transistor, an emitter of the sixth transistor,
Eighth of diode connection of the first polarity to which the emitter is connected
Transistor, an emitter connected to the emitter of the fifth transistor.
A ninth transistor of a first polarity to which the
The first transistor whose emitter is connected to the emitter of the six transistors
Polarity tenth transistor, the seventh and eighth transistors
And a second power supply connected between the common connection base of the
A second input circuit comprising two current sources; and a collector output of the second transistor of the first input circuit.
The force and the correction of the tenth transistor of the second input circuit
Of the first input circuit.
4 transistor collector output and before the second input circuit
The collector output of the ninth transistor is added on the output side.
A current mirror circuit is connected to receive the output of the output side of the current mirror circuit.
Operational amplifier characterized by comprising an output circuit which is continued, the.