JPS59154806A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To improve the power efficiency by amplifying an input by an amplifier element connected to a low voltage power supply at a small signal input and by another amplifier element connected to a high voltage power supply at a large signal input. CONSTITUTION:The 1st amplifier element 5 is connected to the lower voltage power supply 6, the 2nd amplifier element 4 is connected to the high voltage power supply 3 and the emitter of both elements is connected to a common load 2. When the voltage VIN of an input source 1 s lower than the value being the subtraction of a voltage drop decided by diodes 20, 10, 7 from a voltage V1 of the low voltage power supply 6, a transistor 17a drives the amplifier element 5 for attaining amplification by the low voltage source, a bias current flowing to a resistor 14 to drive the amplifier element 4 is absorbed so as to turn off the amplifier element 4 connected to the high voltage source. When the input VIN is larger, the amplifier element 4 is driven conversely, the amplification by the high voltage source is attained and the amplifier element 5 connected to the low voltage source is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to an amplifier circuit (amplifier), and particularly to an amplifier circuit that can improve its power supply efficiency.

(Prior Art) Conventionally, class B push-pull output amplifier circuits are often used in output amplifiers. This is because the power supply efficiency is higher than that of a class A output amplifier circuit.

However, even though it is an 8th class pushpull output amplifier circuit, its maximum power supply efficiency is around 70 inches.

An example of a conventional amplifier is shown in FIG. 1, and the conventional amplifier circuit will be further explained using this.

Reference numeral 1 indicates an input signal source having a voltage Vin connected to an input signal terminal, 2 a load resistor, 3 a power supply having a voltage Vce, and 4 a transistor serving as an amplification element.

The power supply efficiency η of the circuit shown in FIG. therefore,
The Vin-η characteristic is f() as shown in FIG.

As is clear from FIG. 2, the conventional amplifier circuit has the disadvantage that the power supply efficiency deteriorates further when the input signal voltage Vin is small, that is, when the output is small.

Furthermore, as can be understood from the above, conventional amplifier circuits, especially high-output amplifiers, have the disadvantage that high heat is generated as a result of collector loss, making it difficult to design heat dissipation to deal with this.

(Objective) An object of the present invention is to eliminate the drawbacks of the prior art described above and provide an amplifier with high power efficiency.

(Summary) In order to achieve the above object, the present invention includes n amplifying elements (first to nth) each having an input terminal, a grounding terminal, and an output terminal, and an amplifying element connected to the grounding terminal of each amplifying element. a common load; n power supplies connected to the output terminals of each amplifying element to supply voltage; means for supplying a common input signal to the input terminals of each of the amplifying elements; means for switching and operating the corresponding amplifying elements one by one in order from the lowest power supply voltage as the power supply voltage increases from 0;
The power supply voltage connected to the (i-th integer) amplifying element is
+1) It was decided to set it to be lower than the power supply voltage connected to the th.

Further, in the present invention, in order to achieve the above object, the first to nth n
a common load connected to the ground terminal of each amplifying element, n power supplies connected to its output terminal to supply voltage to each amplifying element, and a common input signal. means for supplying the input signal to the input terminal of each of the amplifying elements; and means for switching over and operating the corresponding amplifying elements one by one in order from the lowest power supply voltage as the input signal increases from 0; (1 is an integer from 1 to n-t) The power supply voltage connected to the (t+
1) Set the power supply voltage to be lower than the power supply voltage connected to the
The configuration is such that the input terminal current of the +1)th amplifying element is absorbed.

(Embodiment) FIG. 3 shows a first embodiment of the present invention in which the gain of the circuit is 1 as in the conventional example, and this will be described. In this figure, the same reference numerals as in FIG. 1 indicate the same parts and equivalent parts.

6 is a second power supply of voltage V1, and 3 is a first power supply of voltage Vcc. The relationship between vl and Vce is expressed by the following formula (2): (2) 4.5 is the first and second amplifying element each consisting of a transistor, 7 is the base of the second amplifying element 5, and the input signal A diode 8 which is a unidirectional element connected between the terminals is a resistor connected between the base of the second amplifying element 5 and the second power supply 6 and providing a DC bias to the second amplifying element 5. It is.

The operation of the circuit shown in FIG. 3 is explained by the input signal voltage Vin-
The output currents I, , I will be explained using characteristic diagrams.

At Vin = 0, the second amplification element 5 has:
Resistance 8. A -DC bias is applied via the diode 7 and the input signal source 1. For this reason, this transistor 5 is in an on state.

On the other hand, since no DC bias is applied to the first amplifying element 4, this transistor 4 is in an off state.

In the range where Vln satisfies O<■n<Vt, the second amplifying element 5 continues to be in the on state, so the load resistor 2 is not supplied with power from the power supply 6, as is clear from FIG. A current flows in accordance with the input signal voltage Vin. At this time, the power supply efficiency η of this circuit is determined by the following formula (3): % (3) Vin satisfies (V, -α)≦Vin<Vec (where α indicates the voltage drop of diode 7) In the range, first, when Vin is equal to (■1-α), the base voltage of transistor 5 is maximum, so
The collector current of transistor 5 also becomes maximum.

Furthermore, when Vin rises above (V, -α), the transistor 5 shifts to the off state.

On the other hand, as is clear from FIG. 4, the potential between the base and emitter of the transistor 4, which is the first amplification element, becomes positively biased from the time Vin becomes equal to (V, -α). For this reason, the current 11 supplied from the power supply 3 begins to flow through the load resistor 2.

The power supply efficiency η of this circuit at this time (more precisely, after switching to transistor 4) is expressed by equation (4).

Therefore, the Vin-η characteristic of the circuit in FIG. 3 is +31, (41
From the equation, it becomes as shown in Figure 6. That is, as is clear from the comparison between FIG. 2 and FIG. 6, according to this embodiment,
Its power efficiency can be increased.

In addition, FIG. 5 shows Vin −Vout corresponding to FIG.
(Output voltage) characteristic diagram.

FIG. 7 is a circuit diagram showing a second embodiment of the present invention.

In this figure, the same reference numerals as in FIG. 3 indicate the same parts and equivalent parts.

The operation of the circuit of FIG. 7 is substantially similar to the operation of the circuit of FIG.

However, in the circuit shown in FIG. 3, in a range where the input signal voltage Vin satisfies %Vl<Vin<Vcc, the collector-emitter voltage of the transistor 5 becomes reverse biased. For this reason, the transistor 5 may be destroyed.

Therefore, in the embodiment shown in FIG. 7, in order to prevent this,
A diode 9, which is a unidirectional element, is inserted into the emitter (ground terminal) of the transistor 5.

Note that the diode 10 is added to readjust the on/off operation balance of the transistors 4 and 5 due to the addition of the diode 9.

FIG. 8 is a circuit diagram showing a third embodiment of the present invention.

In this figure, the same reference numerals as in FIG. 7 indicate the same parts and equivalent parts.

As is clear from the figure, 11, 12, and 13 are resistors and diodes inserted between the input terminals and input signal terminals of the first and second amplifying elements 4 and 5, respectively, and 14 is the first amplifying element. This is a DC bias resistor of the first amplification element 4 connected between the input terminal of the element 4 and the first power supply 3.

The operation of the circuit of FIG. 8 is substantially similar to the operation of the circuits of FIGS. 3 and 7.

In the circuit of FIG. 3, the relationship between Vin and Vout is as shown in FIG. As is clear from FIG. 5, at the off-on switching operating voltages of transistors 5 and 4, the Vin-Vout characteristic is such that Vout does not change in response to changes in the stepped state -Vin. As is well known, such a state means that the output is distorted with respect to the input signal, and is, of course, undesirable as an amplifier.

Such an active state occurs because the operation of the transistor 4 is delayed by the forward voltage drop between the base and emitter of the transistor 4, and the transistor 5 also only gradually shifts to the off state.

In order to reduce this stepped state, it is necessary to make the time difference between the ON operation of the transistor 4 and the OFF operation of the transistor 5 close to each other. That is, it is necessary that the transistor 4 be in a state where it is easily turned on.

Therefore, in the embodiment shown in FIG. 8, the DC bias resistor 14
By inserting the transistor 4, the transistor 4 is kept in a semi-conducting state and its on operation is accelerated. Note that the resistors 11 and 12 and the diode 13 are the transistors 4 and 13.
This was added to adjust the balance of the on/off operation of No. 5.

FIG. 9 is a circuit diagram showing a fourth embodiment of the present invention.

In this figure, the same reference numerals as in FIG. 8 indicate the same parts and equivalent parts.

15 is a transistor included in the DC bias circuit of the second amplification element 5.

The operation of the circuit shown in FIG. 9 will be explained.

In a range where the input signal voltage Vin satisfies 0≦Vin<V, a DC bias is applied to the transistor 5. For this reason, this transistor 5 is in an on state. At this time, since the transistor 15 added to the DC bias circuit of the transistor 5 is also in an on state, it operates to sink the base bias current of the transistor 4. That is, the voltage drop across the resistor 14 is
Since it is a dog, the transistor 4 is in a nearly non-biased state and is off.

Next, the input signal voltage Vin is (V, -α)≦Vin<
When the range satisfies Vee, transistors 5 and 1
5 transitions to the off state at about the same time. At this time,
Since the base bias potential of transistor 4 increases rapidly, transistor 4 rises sharply. As a result, the time difference between the OFF operation of the transistor 5 and the ON rotation of the transistor 4 can be made closer than in the embodiment shown in FIG. That is, as a result of being able to further reduce the stepped state, it is possible to significantly reduce distortion of the output with respect to the input signal. The overall operation in FIG. 9 is essentially the same as in FIG. 8.

FIG. 10 is a circuit diagram showing a fifth embodiment of the present invention, which is a modification of the circuit shown in FIG. 8. In this figure, the 8th
The same reference numerals as in the figures indicate the same parts and equivalent parts.

16.17 are transistors added to the base sides of the first and second amplifying elements 4.5, 18.19 are resistors connected to the ground terminals (emitters) of the transistors 16.17, and 21. 20 is transistor 4,1
6. ) shows the diodes inserted into the bias circuits of transistors 5 and 17, respectively.

In this circuit, transistors 16 and 17 are connected to transistors 4 and 5, respectively. Therefore, according to this circuit, the current of the DC bias circuit can be reduced. Using this method means that
This is also often used in conventional B-string output amplification circuits.

Note that the diodes 20 and 21 are transistors 4°16
, are added to balance the on/off operation of the transistor 5.17.

FIG. 11 is a circuit diagram showing a sixth embodiment of the present invention, in which the circuit of FIG. 10 is adapted to perform the circuit operation of FIG. 9. In this figure, the same symbols as in Fig. 10 are the same.
The location and equivalent parts are shown.

In FIG. 11, the output terminal (collector) of the transistor 17a added to the base side of the second amplification element 50 is connected to the base of the transistor 16 added to the base side of the first amplification element 4.

For this reason, similarly to the operation of the circuit shown in FIG. 9, in the range where the input signal voltage Vin satisfies O≦Vin<Vl, the transistors 5, 17! Since L is in the on state, the transistor 17a operates to sink the base bias current of the transistor 16. As a result, transistor 4.16 is in the off state at this time.

Next, when the input signal voltage (■) reaches a range that satisfies (■1-α%V Nagisa■ec), the transistor 5.17a
Transistor 4 transitions to the off state at the same time.
, 16 suddenly transition to the on state.

Therefore, in this circuit, each transistor 4
, 5, 16, 17a can be reduced, and the switching time of transistors 4, 16 and transistor 5.17a can be shortened, making it possible to further reduce the stepped state. It became.

FIG. 12 is a circuit diagram showing a seventh embodiment of the present invention. In this figure, the same reference numerals as in FIG. 7 indicate the same parts and equivalent parts.

22 is a third power source of voltage v2, 6 is a second power source of voltage vI, and 3 is a first power source of voltage Vcc.

This voltage V1. The relationship between V and Vec is as shown in equation (5).

■□＜V2＜Vec・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・ （
5) Also, 23 is a third amplifying element 2 consisting of a transistor.
4 and 25 are input terminals (base) of the third amplification element 23
26 is a resistor connected between the third power supply 22 and the input terminal of the third amplifying element 23, and 27 is the third amplifying element 2.
A diode 28 is a unidirectional element connected to the ground terminal (emitter) of diodes 9 and 27, and a diode 28 is a unidirectional element inserted between the output terminals of diodes 9 and 27.

This circuit corresponds to the switching operation of transistors 4 and 5 in the circuit of FIG. 7 plus one stage of switching operation of transistor 23 iζ.

That is, the diode 28 is for determining the operating order of the third amplifying element 23 and the first amplifying element 4.
In the case of this circuit, the third amplification element 23 starts operating first. Therefore, in this circuit, transistors 5 and 2
The switching operation is performed in the order of 3.4.

The Vin-η characteristic of this circuit is as shown in FIG. 13, assuming that vl and v2 are ]/2Vcc and V4Vcc, respectively. That is, as is clear from the comparison of FIGS. 2, 6, and 13, according to this circuit,
The power supply efficiency can be further improved.

In this embodiment, the switching operation is performed in three stages, but it can be easily inferred from this circuit that the switching operation is performed in four stages, five stages, and so on. It is clear that power supply efficiency can be further improved.

FIG. 14 is a circuit diagram showing an example of application of the present invention, in which a class B push-pull amplifier circuit is configured using the circuit shown in FIG. 11. In this figure, the same reference numerals as in FIG. 11 indicate the same parts and equivalent parts.

29 is the transistor 4, 5, 16゜17a in Fig. 11
is a PNP type, 30 is a lower half-cycle amplification section of the push-pull circuit, 30 is an upper half-cycle amplification section of the push-pull circuit, and 31 is a voltage amplifier that drives the lower and upper half-cycle amplification sections 29 and 30. 32 indicates an AC input signal source.

The operation lζ of this circuit will be explained.

When a signal as shown in FIG. 15(a) is input from the input signal source 32, time t occurs. -1, point A of the voltage amplifying section 31
The potential changes as shown in FIG. 15(b) during the same period. As a result, the potential of line B changes during the same period as shown in FIG. 15(c), so the upper half cycle amplifying section 30 operates and amplifies the upper half cycle of the input signal.

Next, when the signal input becomes negative as at time t1 to t11, the voltage at point A changes as shown in FIG. 15(b) during the same period. As a result, the potential of line B becomes
Since the signal changes as shown in FIG. 5(c), the lower half cycle amplifying section 29 operates to amplify the lower half cycle of the input signal.

Note that the operation of the circuits of the lower and upper half-cycle amplification sections 29 and 30 is similar to the operation of the circuit shown in FIG. 11, so a description thereof will be omitted here.

(Effects) As is clear from the above explanation, in the present invention, when the input signal is a small signal, the amplification element (
When the signal is large, the input signal is amplified by an amplifier connected to a high power supply voltage, so that the power supply voltage is automatically switched according to the magnitude of the input signal.

Therefore, according to the present invention, it is possible to improve power supply efficiency, reduce collector loss, and thereby significantly reduce generation of high heat.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional amplifier circuit, Fig. 2 is a Vin-η characteristic diagram of Fig. 1, Fig. 3, Fig. 7, Fig. 8, Fig. 9, Fig. 10, 11 and 12 are circuit diagrams showing one embodiment of the present invention, and FIGS. 4 and 5 are circuit diagrams showing the operation of the circuit shown in FIG. 3.
Figure 6 shows the Vin-η characteristic diagram in Figure 3, and Figure 13 shows the Vi in Figure 12.
An n-η characteristic diagram, FIG. 14 is a circuit diagram showing an example of application of the present invention, and FIG. 15 is a waveform diagram for explaining the operation of FIG. 14. 1... Input signal source, 2... Load resistance, 3, 6.2
2... Power supply, 4,5.23... First to third amplification elements, 7.9, 10, 13, 20, 21, 24, 25, 2
7.28...Diode, 8, 11, 12, 14,
18, 19.26...Resistance, 15-17.17a...
・Transistor agent Patent attorney Michihito Hiraki 23- Fig. 1 Fig. 2 VIN (V) VCC 31- Fig. 10 Fig. 11 Fig. 12 Fig. 13 → ■ Summer N (V)

Claims (6)

[Claims] (1) n first to nth amplifying elements each having an input terminal, a grounding terminal, and an output terminal; a common load connected to the grounding terminal of each amplifying element; n power supplies connected to its output terminals so that
means for supplying a common input signal to the input terminals of each of the amplification elements; and means for switching over and operating the corresponding amplification elements one by one in order of decreasing power supply voltage (ζ) as the input signal increases from 0; and the first (i is 1
1. An amplifier circuit characterized in that a power supply voltage connected to an (i+1)th amplifying element (an integer from 1 to n-1) is set to be lower than a power supply voltage connected to an (i+1)th amplifying element. (2) The amplifier circuit according to claim 1, wherein at least one of each amplifier element includes a bias resistor connected between its input terminal and output terminal. (3) The amplification according to claim 1 or 2, characterized in that means for preventing current from flowing backward between the first and (i+1)th amplifying elements is provided. circuit. (4) n first to nth amplifying elements each having an input terminal, a grounding terminal, and an output terminal; a common load connected to the grounding terminal of each amplifying element; and supplying voltage to each amplifying element. n power supplies connected to the output terminals thereof, means for supplying a common input signal to the input terminals of each of the amplification elements, and a means for supplying a common input signal to the input terminals of each of the amplification elements, and as the input signal increases from 0, the power supply voltages are arranged in order from the lowest to the lowest. , means for switching and operating the corresponding amplifying elements one by one, and the first one (1 is 1 to n).
When the power supply voltage connected to the (integer up to -1) amplification element is set to be lower than the power supply voltage connected to the (1+1)th amplification element, and the first amplification element conducts, the (i+1)th amplification element becomes conductive. ) An amplifier circuit configured to receive input terminal current of the second amplifier element. (5) The amplifier circuit according to claim 4, wherein at least one of each amplifier element includes a bias resistor connected between its input terminal and output terminal. (6) The amplification according to claim 4 or 5, characterized in that means for preventing current from flowing backward between the first and (1+1)th amplification elements is provided. circuit.