JPH0964661A - Amplifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an amplifier circuit capable of solving the defects of a conventional amplifier circuit by which a signal including GND potential can be inputted, but can not respond to inputs up to power supply voltage and an input enabled voltage range is narrowed in accordance with the reduction of power supply voltage and extending a signal input voltage range to its maximum. SOLUTION: A differential amplifier constituted of the Darling-ton connection of NPN transistors(TRs) 14 to 17, a differential amplifier consisting of the Darlington connection of PNP TRs 1 to 4 and a current mirror circuit constituted of PNP TRs 18 to 21 for changing the direction of an output current are combined. The combination forms an amplifier circuit capable of extending a signal input voltage range from GND potential up to the power supply voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier circuit, and more particularly to an amplifier circuit having a wide input operation range.

[0002]

2. Description of the Related Art A conventional amplifier circuit has a G circuit as shown in FIG.
It has a Darlington-connected differential amplifier composed of PNP transistors so as to enable the input of a signal including the ND potential. (For example, JP-A-60-119109
issue).

Next, the input voltage range of this circuit will be described.

The PNP transistors 1, 2, 3, 4 of FIG.
It constitutes a Darlington connection differential amplifier.

The upper limit value V _{ICM (+)} of the input voltage range is determined by the following equation.

V _{ICM (+)} = V _CC −V _{I (11)} −V _{be (4)} −V _{be (3)} where V _{I (11)} is the output voltage of the current source 11, which is normally shown in FIG.
Since the current mirror circuit is composed of PNP transistors as shown in, the collector of PNP transistor 30
It becomes the voltage between the emitters.

V _{be (4)} is the voltage between the base and emitter of the PNP transistor 4, and V _{be (3)} is the PNP transistor 3.
The voltage between the base and the emitter, V _cc, is the voltage of the power supply terminal 25.

The lower limit value V _{ICM (-)} of the input voltage range is determined by the following equation.

V _{ICM (-)} = V _{be (9)} + V _{be (8)} -V _{be (7)} +
V _{ce (3)} −V _{be (3)} −V _{be (4)} However, V _{be (9)} , V _{be (8)} , V _{be (7)} , V _{be (3)} , V _{be (4)}
Are NPN transistor 9, NPN transistor 8, NPN transistor 7, NPN transistor 3 and N, respectively.
The voltage between the base and emitter of the PN transistor 4 is V
_{ce (3)} is the collector-emitter voltage of the PNP transistor 3.

For example, V _CC = 5v, V _be = 0.75v, V
_{When ce} = 0.2v, VICM ₍₊₎ = 5v−0.2v−0.75v−0.75v =
3.3v V _{ICM (−)} = 0.75v + 0.75v−0.75v + 0.
2v−0.75v−0.75v = −0.55v The input voltage range is shown in FIG.

Usually, in an integrated circuit, the lowest potential (here, G
The potential below ND potential) is not input, so in this conventional example, GND (= 0v) to V _{ICM (+)}
The input voltage range is up to (= 3.3v).

[0012]

[Problems that the Invention is to Solve In this conventional amplifier circuit is to allow input of a signal including a GND potential, above-described V _CC potential side of the input range V _CC -2 V _BE as -
When the power supply voltage V _CC is lowered by being restricted by the voltage of V _ce , there is a problem that the input voltage range becomes narrow.

An object of the present invention is to provide an amplifier circuit that maximizes the input voltage range of a signal.

[0014]

SUMMARY OF THE INVENTION An amplifier circuit of the present invention is a differential amplifier of Darlington connection composed of PNP transistors which are capable of inputting a signal including a ground potential and connected to a power supply terminal through a constant current source. And an amplifier circuit having an active load of a current mirror circuit composed of NPN transistors, which is connected to the differential amplifier of the PNP transistor, enables input of a signal including a power supply potential, and is connected to a ground terminal via a constant current source. And a Darlington connection differential amplifier composed of NPN transistors connected in parallel with the differential amplifier of the PNP transistor, and the NPN transistor by inverting the flowing direction of the output current of the differential amplifier of the NPN transistor. A current mirror circuit composed of PNP transistors connected to the active load And wherein the Rukoto.

Further, the Darlington connection differential amplifier composed of the PNP transistor has a differential amplifier connected to a power supply terminal via a constant current source at the emitter of the first-stage transistor of the differential amplifier. The Darlington connection differential amplifier composed of NPN transistors has a differential amplifier connected to the ground terminal through a constant current source at the emitter of the first-stage transistor of the differential amplifier.

Further, the amplifier circuit of the present invention includes a Darlington connection differential amplifier composed of a PNP transistor which is capable of inputting a signal including a ground potential and is connected to a power supply terminal through a constant current source, and the PNP. In an amplifier circuit having an active load of a current mirror circuit composed of NPN transistors, which is connected to a differential amplifier of transistors,
Darlington connection differential composed of NPN transistors connected to a ground terminal via a constant current source and capable of inputting a signal including a power supply potential and connected by inverting the current direction of the differential amplifier of the PNP transistor It is characterized by having an amplifier and a current mirror circuit composed of a PNP transistor connected to an active load composed of the NPN transistor.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The amplifier circuit of the present invention includes a Darlington-connected differential amplifier composed of PNP transistors capable of inputting a signal including a GND potential and an NPN capable of inputting a signal including a V _CC potential. A Darlington connection differential amplifier composed of transistors and a current mirror circuit serving as a common active load composed of NPN transistors,
It has a current mirror circuit composed of PNP transistors for inverting the flowing direction of the output current of the differential amplifier of the NPN transistors, and is compatible with a wide signal input from the GND potential to the V _CC potential.

[0018]

The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a first embodiment of the present invention.

The PNP transistor 1, the PNP transistor 2, the PNP transistor 3, and the PNP transistor 4 form a Darlington connection differential amplifier, and the NPN transistor 14, the NPN transistor 15, the NPN transistor 16, and the NPN transistor 17 form a Darlington connection differential amplifier. An amplifier is configured, and the NPN transistor 5 and the NPN transistor 6 constitute a current mirror circuit as an active load common to the amplifiers. The NP
The PNP transistor 18 and the PNP transistor 19 are provided to the output of the differential amplifier of the NPN transistor so that the load of the Darlington connection differential amplifier composed of the N transistor is an active load constituted by the NPN transistor.
And PNP transistor 20 and PNP transistor 2
1 constitutes a current mirror circuit, which reverses the direction of the output current and is connected to the active load constituted by the NPN transistor.

The input voltage range at this time is as follows.
The upper limit value V _{ICM (+)} is determined by the differential amplifier circuit composed of NPN transistors. V _{ICM (+)} = V _CC −V _{be (20)} −V _{ce (16) +} V _{be (16) +} V
_{be (17)} However, V _{be (20)} , V _{be (16)} , and V _{be (17)} are PNPs, respectively.
The voltage between the base and emitter of the transistor 20, NPN transistor 16 and NPN transistor 17 is V _{ce (16)}
Is the collector-emitter voltage of the NPN transistor 16.

The lower limit value V _{ICM (-)} of the differential amplifier circuit composed of NPN transistors is V _{ICM (-)} = V _GND + V _{I (27) +} V _{be (16)} + V _{be (17) GND} is GND potential, normally 0v, V _{I (27)} is NPN
It becomes the collector-emitter voltage of the transistor.

The lower limit value V _{ICM (-)} is determined by a differential amplifier circuit composed of PNP transistors.

V _{ICM (-)} = GND + V _{be (9)} + V _{be (8)} -V
_{be (7)} + V _{ce (3)} −V _{be (3)} −V _{be (4)} However, V _{be (9)} , V _{be (8)} , V _{be (7)} , V _{be (3)} , V _{be ( Four)}
Are NPN transistor 9, NPN transistor 8, PNP transistor 7, PNP transistor 3 and P respectively.
The voltage between the base and emitter of the NP transistor 4 is V
_{ce (3)} is the collector-emitter voltage of the PNP transistor 3. Further, the upper limit value V _{ICM (+)} of the differential amplifier circuit composed of PNP transistors is V _{ICM (+)} = V _CC −V _{I (11)} −V _{be (4)} −V _{be (3)} where V _{I (11)} is a voltage between the terminals of the constant current source 11, and in an integrated circuit, a current mirror circuit of a PNP transistor normally constitutes a constant current source, so V _{I (11)} is a voltage between the collector and the emitter of the PNP transistor. V _{be (4)} , V _{be (3)}
Are voltages between the base and emitter of the PNP transistor 4 and the PNP transistor 3, respectively.

FIG. 2 is a diagram showing these relationships. FIG. 2 (a) shows the input voltage range on the differential amplifier side of the Darlington connection of the NPN transistor, and FIG. 2 (b) shows the PNP transistor. The input voltage range on the differential amplifier side of the Darlington connection is shown, and FIG. 2C shows the entire input voltage range, and the input voltage range is obviously widened. Further, in the integrated circuit, it is common to apply no voltage below the minimum voltage (in this case, voltage below the GND potential) or voltage above the maximum potential (in this case, voltage above the V _CC potential). GN as the input voltage range of the circuit
You can input from the D voltage to the power supply voltage.

Obviously, when the power supply voltage is both positive and negative, it is possible to input from the negative voltage of the lowest potential to the positive voltage of the highest potential.

FIG. 3 is a circuit diagram of the second embodiment of the present invention. In this embodiment, an NPN transistor configuration, P
Constant current sources 35, 36, 37 are used as the first-stage transistors of the Darlington differential amplifier circuits of the NP transistor configurations.
38 are provided. In this case, the transconductance g _m of the differential amplifier circuit is larger than that in the first embodiment. Regarding the input voltage range, it is possible to input from the GND potential to the V _CC potential as in the first embodiment.

FIG. 4 is a circuit diagram of the third embodiment of the present invention. In the present embodiment, in the first embodiment, the load of the differential amplifier of the NPN transistor is an active load composed of NPN transistors.
A PNP transistors 18 and 19 and a PNP transistors 20 and 21 constitute a current mirror circuit at the output of the N-transistor differential amplifier, and the direction of the output current is inverted and connected to the active load of the NPN transistor. The direction is directly connected to the active load of the NPN transistor, and the connection between the non-inverting input terminal and the inverting input terminal of the differential amplifier of the NPN transistor and the differential amplifier of the PNP transistor connected in parallel is crossed and connected. Also gives the same behavior.

As described above, according to the present invention, a Darlington connection differential amplifier composed of a PNP transistor capable of inputting a signal including a GND potential and an NPN transistor capable of inputting a signal including a V _CC potential are provided. The output of the differential amplifier of the PNP transistor and the NPN transistor are formed by a current mirror circuit composed of a PNP transistor for inverting the direction of the output current of the Darlington connection of the differential amplifier and the differential amplifier of the Darlington connection of the NPN transistor. The output of the amplifier of
Since they are synthesized at the active load of the N transistor, the differential amplifier of the PNP transistor operates when the input voltage is near the GND potential, and when the input voltage is near the V _CC potential, the NP
The N-transistor differential amplifier operates.

[0029]

The present invention has the effect that it is possible to provide an amplifier circuit which can operate in the maximum input voltage range from the GND potential to the power supply potential.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an input voltage range of the present embodiment, (a) shows an input voltage range of a Darlington connection differential amplifier of NPN transistors, and (b) shows a Darlington connection differential amplifier of PNP transistors. The input voltage range on the side is shown, and (c) shows the entire input voltage range.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional example.

FIG. 6 is a circuit diagram of a conventional example (an example in which a constant current source is replaced with a current mirror circuit of PNP transistors).

FIG. 7 is an explanatory diagram of an input voltage range of a conventional example.

[Explanation of symbols]

 1-4 PNP transistor 5-9 NPN transistor 10 Phase compensation capacitor 11-13 Constant current source 14-17 NPN transistor 18-21 PNP transistor 22 Inversion input terminal 23 Forward rotation input terminal 24 Output terminal 25 Power supply terminal 26 GND terminal 27 Constant current source 28 NPN transistor 29 to 33 PNP transistor 34 to 38 Constant current source

Claims (4)

[Claims] 1. A Darlington connection differential amplifier composed of a PNP transistor which is capable of inputting a signal including a ground potential and is connected to a power supply terminal through a constant current source, and a differential amplifier of the PNP transistor. In an amplifier circuit having an active load of a current mirror circuit composed of an NPN transistor, it is possible to input a signal including a power supply potential, is connected to a ground terminal through a constant current source, and is in parallel with a differential amplifier of the PNP transistor. A Darlington connection differential amplifier composed of NPN transistors connected to each other, and a PNP transistor connected to an active load composed of the NPN transistors by inverting the flowing direction of the output current of the differential amplifier of the NPN transistors. An amplifier circuit having the current mirror circuit described above. 2. A Darlington-connected differential amplifier formed of the PNP transistor includes a differential amplifier connected to a power supply terminal via a constant current source at an emitter of a first stage transistor of the differential amplifier, 2. The amplifier circuit according to claim 1, wherein the Darlington connection differential amplifier composed of NPN transistors has a differential amplifier connected to the ground terminal via a constant current source at the emitter of the first stage transistor of the differential amplifier. 3. A Darlington connection differential amplifier composed of PNP transistors, which is capable of inputting a signal including a ground potential and is connected to a power supply terminal via a constant current source, and a differential amplifier of the PNP transistors. In an amplifier circuit having an active load of a current mirror circuit composed of an NPN transistor, it is possible to input a signal including a power supply potential, is connected to a ground terminal through a constant current source, and is a current of a differential amplifier of the PNP transistor. An amplifier circuit having a Darlington connection differential amplifier composed of NPN transistors connected in a reversed direction and a current mirror circuit composed of a PNP transistor connected to an active load composed of the NPN transistor. . 4. A Darlington connection differential amplifier configured by the PNP transistor includes a differential amplifier connected to a power supply terminal via a constant current source at an emitter of a first-stage transistor of the differential amplifier, 4. The amplifier circuit according to claim 3, wherein the Darlington connection differential amplifier composed of NPN transistors has a differential amplifier connected to the ground terminal through a constant current source at the emitter of the first-stage transistor of the differential amplifier.