JP2600239B2 - amplifier - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier, and more particularly, to a low-shear amplifier operable at a low voltage.

[Conventional technology]

As shown in FIG. 2, a conventional amplifier having a common-emitter amplifier at the last stage connects the emitters of transistors Q ₁ and Q ₂ to a constant current source I ₁ having the other end commonly connected, and a differential amplifier. And the collectors of the transistors Q ₁ and Q ₂ are connected to the transistors Q ₇ and Q ₈ , respectively, which are connected to a common low-voltage source.
Connected to the emitter. The collector of the transistor Q ₇ is collector and base and of the transistor Q _9, is connected to the base of the transistor Q _10. The collector of the transistor Q ₈ is the collector of the transistor Q ₁₁ is connected to the base of the collector of the transistor Q ₁₁ of the transistor Q ₁₀ is connected to a load resistor RL2 other end of which is grounded, the transistors Q _9, Q
_10, the emitter of Q ₁₁ is connected to a direct current V _CC, the input terminal is based T _1, T ₂ of the transistor Q _1, Q _2, the output terminal is constituted by the collector T ₃ of the transistor Q _11. Q ₇ and Q ₈ are grounded base amplifiers, are cascode-connected to a differential amplifier composed of transistors Q ₁ and Q ₂ , constitute an active load by a current mirror composed of transistors Q ₉ and Q _10, and have a grounded emitter amplifier of Q ₁₁ in current-amplified to obtain an output terminal T ₃ of the amplitude by loading PL2 that is a resistance here.

[Problems to be solved by the invention]

The conventional amplifier described above has transistors Q ₁ and Q ₂ , Q ₇
Since the voltage V _CE between the collector and the emitter of each pair of Q ₈ , Q ₉ and Q ₁₀ is the same, it has the characteristic that the collector current of each pair transistor is well-balanced, but since the transistors are stacked vertically in multiple stages, It is difficult to operate at low voltage. If a constant current source I ₁ composed of a grounded emitter transistor in FIG. 2, it is necessary to take approximately 03V the collector-emitter voltage of the low-current source in the I ₁ transistor.
Similarly, the voltage between the collector and the emitter of the transistors Q ₁ and Q ₇ also needs to be 0.3V. The transistor Q ₉ is the collector - base for the base between short - is emitter voltage V _BE 0.7
V is required.

In consideration of the above, the required power supply voltage V _CC is V _CC 2 = 0.3 V + V _{CE (Q1)} + V _{CE (Q7)} + V _{BE (Q9)} = 0.3 V + 0.3 V + 0.3 V + 0.7 V = 1.6 V. In the current mirror circuit including the transistors Q ₉ and Q ₁₀ shown in FIG. 2, since the base current is not corrected, the outflow current is smaller than the inflow current, and the balance state is lost. Therefore, if a Wilcon-type current mirror as shown in FIG. 3 is used, no error due to the base current occurs. However, since the transistors are stacked in two stages with the base-collector short circuit, when this is applied to FIG. In addition, the power supply voltage requires an additional 0.7V 2.
3V.

As described above, the conventional example shown in FIG. 2 requires a power supply voltage of 1.6 V, and a power supply voltage of 2.3 V when a Wilson-type current mirror is used. When trying to operate a circuit at low voltage,
Generally, a battery is used. In that case, it is required that the battery can be used at 1.5 V. In the example shown in FIG. 2,
Since it cannot be used at 1.5V, it is not suitable as a low voltage circuit.

[Means for solving the problem]

The amplifier of the present invention forms a differential amplifier by first and second transistors, and the collectors of the first and second transistors are respectively connected to the first and second constant current sources and the third and fourth transistors.
, The collectors of the third and fourth transistors are connected to the input side and the output side of a current mirror composed of the fifth and sixth transistors, respectively, and the output side of the current mirror is connected to Seventh
And the collector of the common-emitter amplifier of the seventh transistor whose load is RL1 connected to the base of the other transistor.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Transistors Q ₁ and Q
By ₂ and the low current source I ₁ connected to the common emitter constitute a differential amplifier, the base of the transistor Q _1, Q ₂ is an input terminal. The collectors of the transistors Q ₁ and Q ₂ are respectively connected to the constant current sources I ₂ and I ₃ and the emitters of the transistors Q ₃ and Q ₄ whose bases are fixed at a reference voltage. Here, the current values of the constant current sources I ₁ , I ₂ , and I ₃ must satisfy the following conditions so that the differential amplifier including the transistors Q ₁ and Q ₂ operates even in the switching state.

I ₁ <I ₂ , I ₃ I ₂ = I _{3 The} transistors Q ₃ and Q ₄ whose bases are grounded to the differential amplifier including the transistors Q ₁ and Q ₂ are cascode-connected. The respective collectors of the transistors Q ₃ and Q ₄ are connected to the input side and the output side of a current transistor including the transistors Q ₅ and Q _6, and the output side functions as an active load. Its current output in active load is connected to the base of the transistor Q _12, to drive the load RL1 as an emitter-grounded amplifier.

In the amplifier having the configuration shown in FIG. 1, the power supply voltage V _CC required for the operation of the circuit is determined by the transistors Q ₅ and Q ₃ and the constant current source I ₂ . That collector - the V _BE of transistor Q ₅ that between the base has been short-circuited and 0.7V, transistor Q
_If V _CE of ₃ is 0.3 V and the constant current source I ₂ is a grounded emitter type current mirror, a voltage of 0.3 V is required, so the power supply voltage V _CC 1 is V _CC 1 = 0.3 V + V _{CE (Q3)} + V _{BE (Q5)} = 0.3V + 0.3V + 0.7V = 1.3V. The power supply voltage required for the conventional example shown in Fig. 2 is 1.6V
However, it is possible to operate at 1.3V, which is 0.3V lower. This value of 1.3 V is 0.2 V lower than 1.5 V of one battery, and is therefore more suitable for low-voltage operation than the conventional example shown in FIG. In terms of balance, the collector-emitter voltage V _CE of the transistors Q ₁ and Q ₂ , Q ₃ and Q ₄ , Q ₅ and Q ₆ is the same, and the same balance as that of the conventional example shown in FIG. 2 is obtained. Can be Further, when the current mirrors of the transistors Q ₅ and Q ₆ are configured as a Wilson type having no base current error, the power supply voltage is 1.3 V + 1.7 V = 2.0 V, and it can be operated at a voltage 0.3 V lower than the conventional example.

FIG. 4 shows a second embodiment of the present invention. FIG. 4 shows the first
FIG. 2 shows the circuit shown in FIG. Transistors Q ₁₅ and Q ₁₆ and resistors R 1 and R 2 constitute a constant current source, and transistors Q ₅ , Q ₆ , Q ₁₃ and Q ₁₄ constitute a Wilson-type current mirror. Grounded emitter amplifier output consists Darlington-connected transistor of the transistor Q ₂₃ and Q _24, thereby in the same the V _CE of the transistor Q _5, Q _6. Furthermore, the apparent h _FE is increased by Darlington connection of Q ₂₃ and Q _24, it is possible to reduce the error due to base current.

〔The invention's effect〕

As described above, the present invention is operable at a low voltage and has a good balance, and thus has a feature that distortion is small.

[Brief description of the drawings]

1 is a diagram of an embodiment of the present invention, FIG. 2 is a diagram of a conventional example, FIG. 3 is a diagram of a Wilson-type current mirror circuit, and FIG. 4 is a diagram of a second embodiment of the present invention.

Claims (1)

(57) [Claims] A first differential amplifier is constituted by first and second transistors, a common emitter of the first differential amplifier is connected to a first constant current source whose other end is grounded, , Second
The bases of the transistors have first and second input terminals, respectively, and the other ends of the collectors of the first and second transistors are connected to a DC power supply and the other ends of the second and third current sources have the same current value. And the bases are commonly connected to the emitters of third and fourth transistors whose bases are commonly connected to a constant voltage source. The collector of the third transistor is connected to the collector and base of the fifth transistor and the sixth transistor.
The collector of the sixth transistor is connected to the collector of the fourth transistor and the base of the seventh transistor, the emitters of the fifth, sixth, and seventh transistors are grounded, respectively. Seventh
The collector of the transistor is connected to a load RL whose other end is connected to a DC power supply and serves as an output terminal.