JP3413281B2 - Power amplifier circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplification circuit which uses a switching power supply and supplies a power supply voltage corresponding to an input signal voltage to a power amplification transistor.

[0002]

2. Description of the Related Art Such a conventional power amplifier circuit is shown in FIG.
3 is configured. In the figure, 1 is an input I
A voltage amplifier for amplifying the input signal voltage Vin of N, Q
1, Q2 are power amplification transistors of complementary push-pull transistor configuration for power amplification of the output from the voltage amplifier 1, ± B1 is the first power supply voltage, and V1 and V2 are voltage amplifiers 1.
Of the reference voltage sources 2 and 3 connected in series to the output of the switching element, switching elements composed of transistors and FETs for switching the first power supply voltage ± B1, and 4 and 5 are coils L
1, capacitor C1 and coil L2, capacitor C2
Is a low-pass filter configured by smoothing the output voltage of the switching elements 2 and 3.

Reference numerals 6 and 7 compare the absolute value voltage obtained by adding the reference voltages V1 and V2 and the voltage obtained by voltage amplification of the input signal voltage Vin by the voltage amplifier 1 with the voltage passed through the low pass filter, and the difference between them. Comparator circuit that outputs voltage, D
3 and D4 are flywheel diodes.

Outputs from the voltage amplifier 1 are supplied to the bases which are the signal input terminals of the power amplification transistors Q1 and Q2, and the outputs which are the low-pass filters 4 and 5 and the comparison circuits 6 and 7 are connected to the collector which is the power supply terminal. Input is connected, the output OUT is derived from the common emitter, and the output signal voltage Vout is obtained.

In the above configuration, the configuration in the upper part of the figure (voltage amplifier 1, switching element 2, first power supply voltage + B
1, power amplification transistor Q1, low-pass filter 4,
The operation of the comparison circuit 6 and the reference voltage V1) will be described, but the same applies to the configuration in the lower part of the figure.

When the absolute value of the voltage obtained by adding the reference voltage V1 to the voltage obtained by amplifying the input signal voltage Vin by the voltage amplifier 1 is larger than the output voltage from the low pass filter 4, the output of the comparison circuit 6 causes the switching element. 2 turns on. Therefore, the first power supply voltage + B1 is supplied to the low-pass filter 4 through the switching element 2,
The switching output of the power supply voltage + B1 is smoothed and input to the comparison circuit 6. Although the output voltage of the low-pass filter 4 increases during the period when the switching element 2 is on, this output voltage is the absolute value of the voltage obtained by adding the reference voltage V1 to the voltage obtained by amplifying the input signal voltage Vin by the voltage amplifier 1. When it becomes larger than the value, the switching element 2 is turned off by the output of the comparison circuit 6. Therefore, the first power supply voltage + B1 is no longer supplied to the low-pass filter 4, and the output voltage of the low-pass filter 4 decreases. However, when the absolute value voltage becomes higher than this output voltage, the switching element 2 is turned on again and the first power supply is turned on. The voltage + B1 is supplied to the low pass filter 4 through the switching element 2.

Thereafter, by repeating the above operation, feedback is applied so that the two input voltages of the comparison circuit 6 become substantially equal, and the collector of the power amplification transistor Q1 outputs the output of the power amplification transistor Q1 as shown in FIG. A voltage obtained by adding the reference voltage V1 to the signal voltage Vout is supplied to the collector of the power amplification transistor Q1, and this voltage changes following the output signal voltage Vout and the input signal voltage Vin.

At this time, the power amplification transistors Q1 and Q
The collector loss Pc of 2 is smaller than that of a class A amplifier or a class B1 amplifier using a normal fixed power source, and heat generation can be suppressed.

[0009]

However, in such a conventional configuration, noise at the time of switching the switching elements 2 and 3 gets into the amplification circuits such as the power amplification transistors Q1 and Q2 and the voltage amplifier 1 to deteriorate the SN ratio. The problem arises.

Particularly, when the output signal is small, the SN ratio is significantly deteriorated, and it is difficult to obtain satisfactory performance in an amplifier which requires a high SN ratio such as an audio amplifier.

Therefore, an object of the present invention is to provide a power amplifier circuit which suppresses the generation of heat and prevents the deterioration of the SN ratio.

[0012]

Means for Solving the Problems The invention of <br/> made claims 1, wherein in order to solve the above problems, to power-amplifying the input signal
Power amplification transistor, power supply voltage, and the power supply voltage
Switching for switching the control signal according to the control signal
Output voltage from the device and the first switching device
A low-pass filter that slides, and a first group for the input signal voltage.
Output voltage from the low-pass filter
Input voltage is input and both voltages are compared and the difference voltage is
Output it as a control signal to the first switching element
And a first comparison circuit that supplies the
Output voltage from the power supply to the power amplifier transistor power supply.
In the power amplifier circuit that supplies the power supply voltage to the supply terminal
The power supply voltage and the power supply of the power amplification transistor.
It is connected between the supply terminals and switches according to the control signal.
A second switching element, the input signal voltage and a second reference
Compare the voltage and output a signal according to the voltage difference between the two.
This is supplied to the second switching element as a control signal
And a second comparison circuit,
When the output signal voltage is small or there is no signal,
2nd switching element according to the control signal from the 2 comparison circuit
Is turned on and the power supply is turned on through the second switching element.
Voltage is supplied to the power supply terminal of the power amplification transistor
Along with the control signal from the first comparison circuit,
The feature is that the switching element is turned off.
It

The power amplifier circuit of the present invention having such a configuration
According to this, when the voltage obtained by adding the first reference voltage to the input signal voltage is larger than the output voltage from the low pass filter, the first switching element is turned on by the output from the first comparison circuit, and the power supply voltage is switched to the first switching circuit. It is supplied to the low-pass filter through the element, smoothed, and input to the first comparison circuit. When the output of the smoothed low-pass filter becomes larger than the voltage obtained by adding the first reference voltage to the input signal voltage, the first switching element is turned off by the output from the first comparison circuit, and the low-pass filter is electrically charged.
The source voltage is no longer supplied and the low-pass filter output drops. And the low-pass filter output is the input signal voltage
When the voltage becomes smaller than the voltage obtained by adding the first reference voltage to, the first switching element is turned on again by the output from the first comparison circuit, and thereafter , feedback is applied so that the two input voltages of the first comparison circuit become substantially equal, A voltage obtained by adding the reference voltage to the output signal voltage of the power amplification transistor is supplied to the power supply terminal of the power amplification transistor, and this voltage changes following the output signal voltage and the input signal voltage.

When the input signal voltage is smaller than the second reference voltage and the output signal voltage of the power amplification transistor is small or there is no signal, the second switching element is turned on by the control signal from the second comparison circuit, and the second switching element is turned on. The power supply voltage is supplied to the power supply terminal of the power amplification transistor through the two switching elements, the first switching element is turned off by the control signal from the first comparison circuit, and a constant power supply voltage is supplied to the power amplification transistor. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the embodiment shown in FIG. 1, the same parts as those in the configuration of FIG. 3 are designated by the same reference numerals.

± B2 is a second power supply voltage which is smaller than the first power supply voltage ± B1, and the power amplification transistors Q1 and Q2 are connected via the diodes D1 and D2 which are unidirectional elements.
And the low-pass filter outputs of the comparator circuits 6 and 7 are supplied to the input on the side to which the output is applied. This second power supply voltage ±
B2 is, for example, about 1/5 to 1/10 of the first power supply voltage ± B1
Set to a degree.

In the above configuration, the configuration in the upper part of the figure (voltage amplifier 1, switching element 2, first power supply voltage + B
1, power amplification transistor Q1, low-pass filter 4,
The operation of the comparison circuit 6, the reference voltage V1, the second power supply voltage + B2, and the diode D1) will be described, but the same applies to the configuration in the lower stage of the figure.

The absolute value of the voltage obtained by adding the reference voltage V1 to the voltage obtained by amplifying the input signal voltage Vin by the voltage amplifier 1 is a voltage obtained by smoothing the output voltage of the switching element 2 which is the output voltage from the low pass filter 4. When it is larger, the switching element 2 is turned on by the output of the comparison circuit 6. Therefore, the first power supply voltage + B1 is supplied to the low-pass filter 4 through the switching element 2,
The switching output of the power supply voltage + B1 is smoothed and input to the comparison circuit 6. Although the output voltage of the low-pass filter 4 increases during the period when the switching element 2 is on, this output voltage is the absolute value of the voltage obtained by adding the reference voltage V1 to the voltage obtained by amplifying the input signal voltage Vin by the voltage amplifier 1. When it becomes larger than the value, the switching element 2 is turned off by the output of the comparison circuit 6. Therefore, the first power supply voltage + B1 is no longer supplied to the low-pass filter 4, and the output voltage of the low-pass filter 4 decreases. However, when the absolute value voltage becomes higher than this output voltage, the switching element 2 is turned on again and the first power supply is turned on. The voltage + B1 is supplied to the low pass filter 4 through the switching element 2.

By repeating the above operation, feedback is performed so that the two input voltages of the comparison circuit 6 become substantially equal, and the collector of the power amplifying transistor Q1 has the power amplifying transistor as shown in FIG. 2 (a). A voltage obtained by adding the reference voltage V1 to the output signal voltage Vout of Q1 is supplied to the collector of the power amplification transistor Q1, and this voltage changes following the output signal voltage Vout and the input signal voltage Vin.

On the other hand, the input signal voltage Vin is fed to the voltage amplifier 1
When the absolute value of the voltage obtained by adding the reference voltage V1 to the voltage amplified by is smaller than the output voltage from the low-pass filter 4, the output of the comparison circuit 6 turns off the switching element 2. Therefore, the voltage of the second power supply voltage + B2 is supplied to the power amplification transistor Q1 via the diode D1.
2 and the fixed power supply voltage is applied to the collector of the power amplification transistor Q1 as shown in FIG. 2 (b).

That is, the power amplification transistors Q1 and Q2
On the other hand, the output signal voltage Vout can be obtained even when the switching power supply by the switching elements 2 and 3 does not operate until the power supply voltage is supplied by the second power supply voltage ± B2.
It is possible to prevent deterioration of the SN ratio at the time of small output.

FIG. 3 shows a second embodiment according to the present invention,
Connect the reference voltages V1 and V2 to the input side of the voltage amplifier 1,
The voltage attenuators 8 and 9 are connected to the outputs of the low-pass filters 4 and 5 to attenuate the output of the low-pass filter and the comparison circuit 6
7, and other configurations are the same as those in FIG.

When the gain of the voltage amplifier 1 is A in FIG. 3, the attenuation of the voltage attenuators 8 and 9 is 1 / A,
The reference voltages V1 and V2 are set to 1 / A with respect to the reference voltages V1 and V2 of FIG.

In FIG. 3, the collector voltages of the power amplification transistors Q1 and Q2 are A · Vin, which are multiplied by 1 / A by the voltage attenuators 8 and 9 and input signals to the low-pass filter side inputs of the comparison circuits 6 and 7. The voltage Vin is input. Further, the reference voltages V1 and V2 are the reference voltage V of FIG.
The switching elements 2 and 3 are driven so that the two inputs of the comparison circuits 6 and 7 are equal because they are set to 1 / A with respect to 1 and V2 and input to the comparison circuits 6 and 7.

In each of the above-described embodiments, in the embodiment shown in FIG. 1, since the comparison circuits 6 and 7 fully swing to the vicinity of the first power supply voltage ± B1, the comparison circuits 6 and 7 are required to have high withstand voltage.

Further, in the embodiment shown in FIG. 3, since a small voltage is input to the comparison circuits 6 and 7, the comparison circuits 6 and 7 are required to have high precision.

FIG. 4 shows another embodiment according to the present invention in which the above points are improved. In FIG. 4, the input signal voltage Vin is amplified by voltage amplifiers 10 and 11 different from the voltage amplifier 1. The other configurations are the same as those in FIG.

Here, assuming that the gain of the voltage amplifier 1 is A, the gain B of the voltage amplifiers 10 and 11 is set to about 1/20, and the attenuation of the voltage attenuators 8 and 9 is set to B / A. (For example, if A = 100, B = 5, attenuation of voltage attenuator = 1/20).

Therefore, B · Vin is input to the low-pass filter side inputs of the comparison circuits 6 and 7. Further, the input signal voltage Vin is multiplied by B to generate reference voltages V1 and V2 (see FIG.
Is set to 1 / A with respect to the reference voltages V1 and V2 of 1) and is input to the comparison circuits 6 and 7, so that the two inputs of the comparison circuits 6 and 7 become equal to each other. 3 are driven.

FIG. 5 shows another embodiment according to the present invention,
The same parts as those in FIG. 1 are designated by the same reference numerals.

In FIG. 5, the second power supply voltage ± B of FIG.
2 and the diodes D1 and D2 are omitted, and the following configuration is added. The first power supply voltage ± B1 will be simply referred to as power supply voltage ± B1 below.

Reference numerals 12 and 13 denote input signal voltage Vin, respectively.
And a pair of positive and negative reference voltages V3, V4 and outputs a control signal corresponding to the difference voltage, a pair of comparison circuits 14,
15 is connected between the power supply voltage ± B1 and the collectors of the power amplification transistors Q1 and Q2, respectively, and is connected to the comparison circuits 12 and 1
3 is a pair of switching elements that switch according to the control signal from the control unit 3.

In the above configuration, a case where the output signal voltage Vout obtained from the common emitter of the power amplification transistors Q1 and Q2 is small or no signal is output will be described.

When the output signal voltage Vout is small, the input signal voltage Vin voltage-amplified by the voltage amplifier 1 becomes smaller than the reference voltages V3 and V4, and the comparison circuits 12 and 1
The switching elements 14 and 15 are turned on by the control signal from 3.

Further, the absolute value of the voltage obtained by adding the reference voltages V1 and V2 to the input signal voltage Vin voltage-amplified by the voltage amplifier 1 is smaller than the collector voltage of the power amplification transistors Q1 and Q2. Is turned off.

Therefore, the power amplification transistor Q1,
As shown in FIG. 6, the power supply voltage ± B1 is supplied to the collectors of Q2 through switching elements 14 and 15.
At this time, since the switching elements 2 and 3 are off, switching noise is not generated.

Further, since the level at which the switching elements 14 and 15 are turned on is small, the power amplification transistor Q1,
The loss of Q2 also does not increase.

On the other hand, when the output signal voltage Vout becomes large to some extent, the input signal voltage Vin voltage-amplified by the voltage amplifier 1 becomes larger than the reference voltages V3 and V4, and the switching elements 14 and 13 are controlled by the control signals from the comparison circuits 12 and 13. 15 turns off.

As described with reference to FIG. 1, the comparison circuits 6 and 7 are fed back so that the two input voltages become equal by the ON / OFF driving of the switching elements 2 and 3, and the power amplification transistors Q1 and Q2 are fed back. A power supply voltage that follows the output signal voltage Vout and the input signal voltage Vin is supplied to each collector.

7 and 8 show other embodiments of the present invention, respectively, and the same portions as those in FIGS. 3 and 4 are designated by the same reference numerals.

In FIGS. 7 and 8, the second power supply voltage ± B2 and the diodes D1 and D2 in FIGS. 3 and 4 are omitted, and the pair of comparison circuits 12 and 13 described in FIG.
And a pair of positive and negative reference voltages V3 and V4 and a pair of switching elements 14 and 15 are added.

In the above configuration, when the output signal voltage Vout obtained from the common emitter of the power amplification transistors Q1 and Q2 is small, or when there is no signal output,
As described above, the input signal voltage Vin that is voltage-amplified by the voltage amplifier 1 becomes smaller than the reference voltages V3 and V4, the switching elements 14 and 15 are turned on by the control signals from the comparison circuits 12 and 13, and the voltage is increased by the voltage amplifier 1. Since the absolute value of the voltage obtained by adding the reference voltages V1 and V2 to the amplified input signal voltage Vin is smaller than the collector voltage of the power amplification transistors Q1 and Q2, the switching elements 2 and 3 are
Is turned off.

As a result, the power amplification transistor Q1,
A power supply voltage ± B1 is supplied to each collector of Q2 through switching elements 14 and 15.

On the other hand, when the output signal voltage Vout becomes large to some extent, the input signal voltage Vin voltage-amplified by the voltage amplifier 1 becomes larger than the reference voltages V3 and V4 as described above, and the control signals from the comparison circuits 12 and 13 make it possible. The switching elements 14 and 15 are turned off.

Further, as described with reference to FIGS. 3 and 4, the comparator circuits 6 and 7 are fed back so that the two input voltages become equal by the ON / OFF driving of the switching elements 2 and 3, and the power amplification transistor Q1. , Q2 is supplied with a power supply voltage that follows the output signal voltage Vout and the input signal voltage Vin.

Thus, in the embodiments shown in FIGS. 5, 7 and 8, when the input signal voltage Vin such that the collector power supply voltage follows the output signal voltage Vout is continuously input, the output signal voltage Vout. The switching elements 14 and 15 may be repeatedly turned on and off for each wave of, and switching noise may be generated by the switching elements 14 and 15.

9 to 11 show an embodiment in which means for preventing the generation of such switching noise is added.

FIG. 9 shows a comparison circuit 1 in the configuration of FIG.
The outputs from 2 and 13 are input to the delay circuits 16 and 17, and the outputs from the delay circuits 16 and 17 are supplied to the switching elements 14 and 15 as control signals.

Similarly, FIGS. 10 and 11 are similar to FIGS.
In the above configuration, delay circuits 16 and 17 are provided between the control signals input to the comparison circuits 12 and 13 and the switching elements 14 and 15, respectively.

In the above structure, the switching element 1
When an input signal voltage Vin of a level such that 4 and 15 are repeatedly turned on and off is input, the delay circuits 16 and 17 cause the comparison circuits 12 and 13 to switch to the switching elements 14 and 1.
This is delayed for control signals that cause 5 to go from off to on.

After the elapse of this delay time, the level of the input signal voltage Vin is sufficiently high, and the comparison circuit 1
Since the control signals for turning on the switching elements 14 and 15 are generated from the switching elements 2 and 13, the switching elements 14 and 15 are turned on.
Reference numeral 15 maintains the off state with respect to such an input signal voltage Vin, and the collector power supply voltages of the power amplification transistors Q1 and Q2 change following the output signal voltage Vout by the action of the switching elements 2 and 3.

Therefore, the switching elements 14 and 15
It is possible to prevent the generation of noise due to the switching of.

On the other hand, the input signal voltage Vi having a small signal level such that the switching elements 14 and 15 are maintained in the ON state.
When n is input, or when there is no signal, the comparison circuits 12 and 13 output control signals for turning on the switching elements 14 and 15 through the delay circuits 16 and 17 to turn on the switching elements 14 and 15. And the switching elements 2 and 3 are maintained in the off state.

FIG. 12 shows a specific example of the delay circuits 16 and 17, which is constituted by a low-pass filter in which a series circuit of a resistor R1 and a diode D5 and a resistor R2 are connected in parallel, and a capacitor C3 is connected between the output side and the reference potential. Has been done.

The low pass filters 16 and 17 are
, The output and switching element 14,
Connect a buffer between 15.

A control signal for turning on the switching elements 14 and 15 from off to on in the positive direction is a signal which rises in the positive direction from the comparison circuits 12 and 13. When this signal is input to the low pass filter, the diode D5 is turned on and the resistance is increased. R
1 and R2 are connected in parallel, and rise with a time constant set by the parallel resistance value of R1 and R2 and the capacitor C3.

Further, a control signal for turning off the switching elements 14 and 15 from ON to ON is a signal which falls in the negative direction. When this signal is input to the low pass filter, the diode D5 is turned OFF and the resistance of the resistor R1 is reduced. It falls at the time constant set by the value and the capacitor C3.

Therefore, the low-pass filters 16 and 17
Rise time (attack time) and fall time (recovery time) are set to be different so that the rise time is shorter than the fall time (for example, the rise time is 0 to several tens to 100 ms).
ec, the fall time is set to about 25 msec and 50 msec).

If the rise time is set too long, the time during which the switching elements 14 and 15 are always on becomes long, and the rise time is set in consideration of suppressing an increase in heat generation.

Further, the fall time is about 20 Hz, which is the lowest audible frequency of the audio signal, with respect to the input signal voltage Vin at which the switching elements 14 and 15 are repeatedly turned on and off. It is set to a value such that 15 does not operate on / off.

[0061]

As described above, according to the present invention, it is possible to suppress generation of heat from the amplifier and prevent deterioration of the SN ratio.

Further, the power supply voltage can be constituted by one power supply.

Further, it is possible to suppress the occurrence of switching noise when the input signal voltage is a small signal or no signal.

[Brief description of drawings]

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

FIG. 2 is a diagram showing voltage waveforms in FIG.

FIG. 3 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 4 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 5 is a diagram showing an embodiment of a power amplifier circuit according to the present invention.

FIG. 6 is a diagram showing voltage waveforms in FIG.

FIG. 7 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 8 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 9 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 10 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 11 is a diagram showing another embodiment of the power amplifier circuit according to the present invention.

FIG. 12 is a diagram showing an embodiment of the delay circuit in FIGS. 9 to 11.

FIG. 13 is a diagram showing an example of a conventional power amplifier circuit.

FIG. 14 is a diagram showing voltage waveforms in FIG. 13.

[Explanation of symbols]

1 voltage amplifier Q1, Q2 power amplification transistor ± B1 1st power supply voltage ± B2 Second power supply voltage V1, V2 reference voltage source A few switching elements 4,5 low pass filter 6, 7 Comparison circuit 8, 9 Voltage attenuator 10, 11 voltage amplifier 12, 13 Comparison circuit 14, 15 switching elements 16,17 Delay circuit V3, V4 reference voltage source D1, D2, D5 diodes D3, D4 flywheel diode

Claims (11)

(57) [Claims] 1. A power amplification transistor for power-amplifying an input signal, a power supply voltage, and a first switch for switching the power supply voltage according to a control signal.
A switching element, a low-pass filter that smoothes an output voltage from the first switching element, a voltage obtained by adding a first reference voltage to the input signal voltage, and an output voltage from the low-pass filter are input, and both voltages are compared. And a first comparison circuit that outputs the difference voltage and supplies it to the first switching element as a control signal, and supplies the output voltage from the low-pass filter to the power supply terminal of the power amplification transistor as the power supply voltage. A power amplifying circuit that is connected between the power supply voltage and a power supply terminal of the power amplifying transistor and switches according to a control signal.
A switching element; and a second comparison circuit that compares the input signal voltage with a second reference voltage, outputs a signal corresponding to a voltage difference between the two, and supplies the signal to the second switching element as a control signal. When the output signal voltage of the power amplification transistor is small or there is no signal, the second switching element is turned on by the control signal from the second comparison circuit and the power supply voltage is supplied to the power amplification transistor through the second switching element. A power amplifier circuit characterized in that the first switching element is turned off by a control signal from the first comparison circuit while being supplied to a terminal. 2. A power amplification transistor having a complementary push-pull transistor configuration for power-amplifying an input signal, positive and negative power supply voltages, and a pair of first switching elements for switching the positive and negative power supply voltages according to a control signal. A pair of low-pass filters that smooth the output voltage from the pair of first switching elements, a voltage obtained by adding a positive and negative first reference voltage to the input signal voltage, and an output voltage from the pair of low-pass filters are input. And a pair of first comparison circuits that output the difference voltage as a control signal to the pair of first switching elements, and output the output voltage from the pair of low-pass filters to the complementary type. A power amplifier circuit that supplies power supply voltage to each power supply terminal of the power amplifier transistor of push-pull transistor configuration. A pair of second switching elements that are respectively connected between the positive and negative power supply voltages and the power supply terminals of the power amplification transistor and switch according to a control signal, and the input signal voltage and the positive and negative second reference voltages are compared. And a pair of second comparison circuits that respectively output signals corresponding to the voltage difference between the two and supply the signals as control signals to the pair of second switching elements, respectively, and output signal voltage of the complementary power amplification transistor. Is small or there is no signal, the pair of second switching elements are turned on by the control signal from the pair of second comparison circuits, and the power supply voltage is supplied to the power supply terminal of the complementary power amplification transistor through the second switching element. The pair of first switching elements are supplied with the control signals from the pair of first comparison circuits. Power amplifier circuit is characterized in that so as to turn off. 3. A power amplifier circuit according to claim 1 or 2, wherein the input signal voltage to the voltage amplifying comprises a supply voltage amplifier this voltage amplified output to the signal input terminal of said power amplifying transistor, said first A power amplifier circuit, wherein the reference voltage is added to the output of the voltage amplifier. 4. The power amplifier circuit according to claim 1, wherein the input signal voltage is voltage-amplified, and the voltage-amplified output is supplied to the signal input terminal of the power-amplifying transistor; the low-pass filter output; And a voltage attenuator provided between inputs of one comparison circuit, wherein the first reference voltage is added to an input signal voltage of the voltage amplifier. 5. The power amplifier circuit according to claim 2, wherein the input signal voltage is voltage-amplified, and a voltage amplifier that supplies the voltage-amplified output to a signal input terminal of the power-amplifying transistor, and the pair of low-pass filters. A pair of voltage attenuators provided between each output and a pair of inputs of the first comparison circuit, wherein the positive and negative first reference voltages are added to the input signal voltage of the voltage amplifier. Power amplifier circuit. 6. The power amplifier circuit according to claim 1, wherein the input signal voltage is voltage-amplified, and the voltage amplified output is supplied to a signal input terminal of the power amplifier transistor.
A voltage amplifier; a voltage attenuator provided between the low-pass filter output and a first comparison circuit input; and a second voltage amplifier different from the first voltage amplifier that amplifies the input signal voltage, A power amplifier circuit, wherein one reference voltage is added to the output voltage of the second voltage amplifier. 7. The power amplification circuit according to claim 2, wherein the input signal voltage is voltage-amplified, and the voltage-amplified output is supplied to a signal input terminal of the power-amplification transistor.
A voltage amplifier, a pair of voltage attenuators provided between the pair of low-pass filter outputs and a pair of first comparison circuit inputs, and a pair of second voltage amplifiers different from the first voltage amplifier that amplifies the input signal voltage. A voltage amplifier, wherein the positive and negative first reference voltages are added to the output voltages of the pair of second voltage amplifiers, respectively. 8. The power amplification circuit according to claim 1, further comprising a delay circuit between the output of the second comparison circuit and the control signal input of the second switching element. 9. The power amplifier circuit according to claim 2, wherein a pair of delay circuits are provided between the outputs of the pair of second comparison circuits and the pair of second switching element control signal inputs, respectively. Amplifier circuit. 10. The power amplification circuit according to claim 1, wherein the delay circuit is composed of a low-pass filter and is set so that its rise time and fall time are different from each other. circuit. 11. The power amplification circuit according to claim 10, wherein the rise time is shorter than the fall time.