KR830001934B1 - Push-pull amplifier circuit - Google Patents

Abstract

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Description

Push-pull amplifier circuit

1 is a circuit diagram illustrating the principles of the present invention.

2 is a circuit diagram showing one embodiment of the present invention.

3 is a circuit diagram showing another embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifying circuit, in particular, to a push-pull amplifying circuit using a bipolar transistor.

Since the amplification circuit needs to minimize the distortion in the amplification output, a method of suppressing the distortion by adding negative feedback is widely accepted.

However, the reduction of amplification degree cannot be avoided by adding negative feedback. Therefore, in order to obtain a desired amplification degree, not only many amplification elements or amplification circuits are required, but also the stability of the whole amplification circuit deteriorates and there is a risk of showing oscillation. .

Particularly, in the transistor which is an amplifying element, since the input / output characteristics between meters are nonlinear in the base, a large current is flowed or a negative feedback is added to improve this nonlinearity. In particular, the solution by negative feedback will have the above drawbacks.

An object of the present invention is to provide a push-pull transistor amplifier circuit capable of improving nonlinear distortion of an amplifying transistor without adding negative feedback.

The push-pull amplification circuit of the present invention comprises a first transistor to which an input signal is applied to a base, an output of the first transistor as a base input, and a second transistor of reverse conductivity type to the first transistor and these transistors. One amplifier composed of a means for supplying a maintenance current and a phase-symmetric type having the same conductivity type as that of each of the amplifiers and a transistor complementary to each transistor of the amplifier. I) an amplifier is provided so that the base of the first transistor of both amplifiers is driven by the same input signal, and the predetermined load is driven in accordance with the current flowing through the input or output transistors, respectively.

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

FIG. 1 is a circuit diagram for explaining the principle of the present invention, and includes a first amplifier 1 and a second amplifier 2 that is complementary to this amplifier. The first amplifier 1 has an NPN transistor Q ₂ having the emitter output of the PNP transistor Q ₁ having an emitter fllower configuration as a base input, and the emitter of this transistor Q ₂ is It is connected to the negative power supply (-B ₃ ) via the emitter resistor R ₁ .

The perlator of the input transistor Q ₁ is directly connected to the negative power supply (-B ₂ ). For example, a current mirror circuit is provided to supply a constant ratio of currents I ₁ and I ₂ to both transistors Q ₁ and Q ₂ , respectively.

The mirror circuit is made up of PNP transistors (Q _3, Q ₄₎ and each of the emitter resistors (R _2, R ₃₎ each have a base commonly connected as shown in the figure, the transistor (Q ₄₎ is connected to the diode. By selecting the resistors R ₂ and R ₃ , the supply current ratio I ₁ / I ₂ to the transistors Q ₁ and Q ₂ can be set to a desired value of 1 / α (α is constant). In this example, the voltage across the emitter resistor R ₂ of the transistor Q ₄ is defined as the output V _OUT1 .

The second amplifier, which is complementary to the _first amplifier, is a complementary element to each of the transistors Q ₁ to Q ₄ of the transistors Q ₅ to Q ₈ . is completely equal to the amplifier (1) and the transistors (Q _7, Q ₈₎ and the emitter resistance by (R _5, R ₆₎ and a current mirror circuit (4) as a current supply means comprises a transistor (Q _5, The ratio of the currents I ₃ , I ₄ to Q ₆ ) is equally set.

In such a configuration, the first amplifier 1 is considered.

If the voltage between the base _{actuators of the} transistors Q ₁ and Q ₂ is V _BE1 and V _BE2 , the difference is established.

I ₂ = (V _IN + V _BE1 -V _BE2 + B ₃ ) R ₁ . … … … … … … … … … … … … … … … … … … … … … (One)

Here, in general, the relationship between the collector current (IC) of the transistor and V _BE is represented by the following equation.

Where q is the electron charge, k is the Boltzmann constant, T is the absolute temperature, and Is is the base-emitter reverse saturation current. Therefore, (V _BE1 -V _BE2 ) in (1) becomes the following equation from (2).

T ₁ is the base-emitter junction temperature of Q ₁ , and T ₂ is the base-emitter junction temperature of Q ₂ . Since Is is a transistor-specific integer, Is ₂ = beta Isl (β is constant). Also, Is is very small, and if sufficient collector current is allowed to flow, Ic / IS >> 1 is established, so the following equation is obtained.

In formula (4), if the junction temperature of the transistor is constant

When (5) becomes constant, let R be the following formula (1).

I ₂ = (V _IN + B ₃ + r) / R ₁ ... … … … … … … … … … … … … … … … … … … … … … … … … … (6)

Therefore, output V _OUT1 is displayed in the following way.

The following formula holds similarly with respect to the second amplifier 2.

의 2배로 되며 또한 트랜지스터의 V_BE에 전혀 무관계가 되어 왜곡이 역압되는 것이 된다. 더우기 푸쉬풀 구성에 있어서는 주지와 같이 우수차 고조파왜곡(偶敎次高調波歪曲)이 저감되므로 보다 한층의 왜곡개선이 가능하게 된다. 즉, 각 증폭기 단체(單體)구성에서는, (7) 또는 (8)식에 나타내는 바와 같이 V_BE에 무관계로 되어 있으나, 실제에는 트랜지스터의 특성상에 분산이나 베이스 전류의 상이(相異) 등에 의하여 아직 완전히 왜곡의 역압은 꾀할 수 없지만, 본예와 같이 푸쉬풀 구성으로 하는 것에 의하여 보다 완전히 왜곡의 저감이 가능하게 된다.Here, if R ₁ = R ₄ , R ₂ = R ₅ , the outputs V _OUT1 and V _OUT2 of these two amplifiers are synthesized in an appropriate manner, and the load is push-pull driven, so that the gain of the entire push-pull amplification circuit is obtained. The benefits of

It is doubled, and has no relation to the V _BE of the transistor, so that the distortion is reversed. In addition, in the push-pull configuration, the even-order harmonic distortion is reduced, as is well known, so that further distortion improvement is possible. That is, in each amplifier unit structure, as shown in (7) or (8), it is irrelevant to V _BE , but in practice, due to dispersion or difference in base current due to transistor characteristics, etc. The back pressure of the distortion is not yet fully achieved, but by the push-pull configuration as in the present example, the distortion can be reduced more completely.

As a method of taking out the output, a change in the current flowing through the transistors Q ₂ and Q ₆ may be taken out. Therefore, the collector and the current supply means 3 of the transistors Q ₂ and Q ₆ are not limited to the example shown in the drawing. The resistors may be inserted between 4) and the voltages across the resistors may be used as outputs. If the amplification degree is not required, the voltage across the emitter resistors R ₁ and R ₄ may be used as the output. In addition, since the current flowing through the transistors Q ₂ and Q ₆ flows in the same ratios to the transistors Q ₁ and Q ₅ by the current mirror circuit, the resistors to the collectors or emitters of the respective transistors Q ₁ and Q ₅ are resisted. It is also possible to insert these and use both voltages as the output.

FIG. 2 shows an example of a circuit for pushing-load driving a load (not shown) by combining the outputs of the amplifiers 1 and 2 of the circuit of FIG. An NPN transistor Q ₉ having a base commonly connected to the base of the transistor Q ₄ of the current mirror circuit 3 of the amplifier 1 is provided, and the emitter of this transistor is positively passed through the resistor R ₇ . It is connected to a positive power source, and the collector is grounded through a reference bias generation source E ₁ and a resistor R ₉ . An NPN transistor Q ₁₀ having a base connected in common to the base of the transistor Q ₈ of the other current mirror circuit 4 is provided, and the emitter of this transistor is negative through the resistor R ₈ . It is connected to a power supply, and the collector is grounded via a reference bias generation source E ₂ and a resistor R ₉ . The collector outputs of these transistors Q ₉ and Q ₁₀ are used as base drive signals of the output push-pull driving transistors Q ₁₁ and Q ₁₂ .

The emitters of the NPN transistor Q ₁₁ and the PNP transistor Q ₁₂ are commonly connected at the output point to each other via emitter resistors R ₁₀ and R ₁₁ to push-pull a predetermined load.

Herein, if the ratio of the currents flowing through the transistors Q ₉ and Q ₄ is set to a constant Iα, the voltage of the common base line of the current mirror circuit 1 is also satisfied in formula (1). V _B ) becomes the following equation.

V _B = + B ₁ -V _BE4 -I ₂ R ₂ . … … … … … … … … … … … … … (9)

By using equation (1) and summarizing equation (9), the following equation is obtained.

(V_IN+V_BE1-V_BE2+B₃)……………………(10)V _B = + B ₁ -V _BE4-

(V _IN + V _BE1 -V _BE2 + B ₃ ). … … … … … … … 10

In addition, the supply current I ₃ from the transistor Q ₉ to the resistor R ₉ is represented by the following equation.

I ₃ = (+ B ₁ -V _BE9 -V _B ) / R ₇ . … … … … … … … … … … … … … (11)

Therefore, the base voltage V ₁ of the transistor Q ₁₁ becomes a difference.

(+B₁-V_BE9-V_B)+E₁…………………………(22)V ₁ = I ₃ , R ₉ + E ₁ =

(+ B ₁ -V _BE9 -V _B ) + E ₁ ... … … … … … … … … … (22)

Substituting this into (10) yields the following equation.

………(13)

… … … (13)

In formula (13), (V _BE1 -V _BE2 ) is a _{constant value} γ from (5), and (V _BE4 -V _BE9 ) is represented by the same _formula .

……………………………………(14)

… … … … … … … … … … … … … … (14)

Β 'is the Is ratio of the transistors Q ₉ and Q ₄ .

Since the transplantation is also a constant value, let γ be the following equation.

………………………(15)

… … … … … … … … … (15)

In addition, the following equation holds for the base voltage V ₂ of the transistor Q ₁₂ of the second amplifier 2.

………………………(16)

… … … … … … … … … (16)

This bias voltage (E ₁ and E ₂₎ of each transistor (Q ₁₁₎ of the V _BE12 and resistance (R ₁₁₎ Chemistry of the voltage (和) and a transistor (Q ₁₂₎ of the V _BE12 and a resistor (R ₁₁₎ in the By selecting so as to be equal to the voltage, E ₁ and E ₂ of the formulas (15) and (16) are erased, respectively, to obtain the push-pull output voltage V _OUT . This output voltage V _OUT also reduces distortion regardless of V _BE of the amplifying transistor.

If R ₁ = R ₄ , R ₂ = R ₅ , and R ₇ = R ₈ , it can be seen that the gain of the circuit is obviously doubled from a single configuration from equations (15) and (16). The offset voltage of the output voltage V _OUT also becomes zero volts, which is convenient.

3 is a circuit diagram showing another embodiment of the present invention, in which parts equivalent to those of FIG. 1 are denoted by the same reference numerals. In this example, the base bias power supplies E ₃ and E ₄ are provided at the respective bases of the transistors Q ₁ and Q _{5 at the} input stages, respectively, and the input resistors R ₁₂ are respectively provided, which makes the collectors of both transistors common. In addition, the common connection point is the push-pull output stage, which is common to the emitter resistors R ₁ and R ₄ of the output transistors Q ₂ and Q ₆ . The offset of (V _OUT ) is set to zero volts.

Further, the current mirror circuit 3, counsel the additional degree (精度) improvement of the PNP transistor (Q ₁₃₎ and NPN transistor (Q ₁₄₎ different from the current mirror output in (4) of each transistor (Q _1, Q _2, The ratio of the supply current to Q ₇ and Q ₈ ) is set to be exactly positive, so that the distortion of V _BE of each transistor can be more completely eliminated.

In this embodiment, the amplification gain is simply "1" due to the emitter follower. However, when used as a B-class push-pull, there is no nonlinearity caused by the distortion of V _BE . There is an advantage that does not occur.

As described above, according to the present invention, distortion due to the voltage between the base and the emitter of the transistor can be reduced and even-order harmonic distortion can be eliminated, so that a significant distortion can be suppressed as compared with a general push-pull circuit.

Moreover, in each of the above embodiments, although a current mirror circuit is used for supplying current to each transistor, a circuit configuration having a function equivalent to that of the current mirror circuit can be used.

Claims (1)

The output of the first transistor and the first transistor to which the input signal is applied to the base is used as the base input, and the second transistor of the reverse conduction type and the first transistor and the first and second transistors have a constant ratio of current to the first transistor. A first amplifier comprising a first transistor, a third transistor having an input signal applied to a base, and having a reverse inversion with the first transistor, and an output of the third transistor as a base input; And a second amplifier comprising a fourth transistor of a reverse conductivity type and a means for supplying a constant ratio of current to the third and fourth transistors, wherein the first and third transistors or the second and fourth transistors are included. A push-pull amplification circuit, characterized in that for driving a predetermined load in accordance with the current flowing through each.

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