JPS626362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power amplification device, and particularly to a power amplification device that performs BTL operation using a pair of power amplifiers.

BTL (Balanced
TRANSFORMERLESS)) The power amplifying device for performing the operation is as shown in FIG.
A single-ended push-pull circuit 1 consisting of a composite NPN transistor consisting of transistors 2 and a composite PNP transistor consisting of transistors 13, 14 and 15, and a pair of power amplifiers of circuit 1' having the same configuration are connected to the earth line (ground terminal 5). They are connected symmetrically. drive transistor 10,
The base of 10' is connected to the input terminals 2, 2', the emitter is grounded, and the collector is connected to the reverse diode 9, 9', 8, 8', 7, 7' and the resistor 6, 6'. are connected in series to the power supply terminals 3, 3' and to the bases of the transistors 13, 13'. This transistor 13,
The collector of transistor 13' is connected to the bases of transistors 14 and 14'.
The emitters of transistors 15 and 15' are connected to the bases of transistors 15 and 15', and the emitters of transistors 15 and 15' are grounded.
The emitter of 13', the collectors of 14 and 14', and the collectors of 15 and 15' are connected to output terminals 4 and 15, respectively.
4'. Moreover, the diode 7,
The connection point between 7' and resistors 6 and 6' is the transistor 11,
11' and is connected to the base of transistor 1.
The emitters of 1 and 11' are transistors 12 and 1.
2' and is connected to the base of transistor 1
The emitters of transistors 2, 12' are connected to output terminals 4, 4', and transistors 11, 11' and 1
Collectors 2 and 12' are connected to power supply terminals 3 and 3'. Transistors 11, 11' and transistors 12, 12' constitute a composite NPN transistor, and transistors 13, 13', transistors 14, 14', and transistors 15, 15' constitute a composite PNP transistor.
The transistor can be replaced with one PNP transistor, but if it is difficult to obtain a PNP transistor with a large current amplification factor at large currents (for example, when it is formed using a semiconductor integrated circuit), the power amplifiers 1 and 1' are the first
It is common to have a configuration as shown in the figure.

Using a pair of conventional power amplifiers like this
In a power amplifier that performs BTL operation, input signals of opposite phase and the same amplitude are applied to input terminals 2 and 2', and after being amplified by a pair of power amplifiers, output terminals 4 and 2' are amplified.
4' output signals of opposite phase and the same amplitude are obtained to drive the load resistor R _L connected between the output terminals 4 and 4', and during operation, the composite NPN transistor 11-1
2,11'-12' and composite PNP transistor 13-
14-15, 13'-14'-15' alternately turn on and off, but composite NPN transistors 11-12 (composite PNP transistor 13-
14-15) are on, the composite NPN transistors 11'-12' (compound PNP transistor 1
3'-14'-15') is off and is a composite of the former.
When the NPN transistors 11-12 (composite PNP transistors 3-14-15) are off, the latter composite NPN transistors 11'-12' (composite PNP transistors 3-14-15) are off.
Transistors 13'-14'-15') are on. Normally, when a transistor transitions from an off state to an on state, there is a so-called turn-off delay time corresponding to the time required for charge to accumulate in the emitter junction, base region, etc. due to the base drive current, and this delay time To make it smaller, increase the base current (for example, use constant voltage drive)
It can be made quite small. However, when using a three-stage directly connected composite PNP transistor as shown in Figure 1,
Composite PNP transistor 14-15, 14'-1
5' base drive current is PNP transistor 13,
Since it is supplied from the collector of 13', it is driven by a constant current, and the turn-on delay time tends to be long. Therefore, if you observe the output waveforms of the pair of power amplifiers relative to the ground, they will be as shown in A and A' in Figure 2, and the output waveform between both ends of the load resistor R _L (waveform at output terminal 4 relative to output terminal 4') The composite PNP transistor 13- is shown in Figure 2B.
When 14-15, 13'-14'-15' are turned on from off, so-called notching distortions A and A' occur due to the turn-off delay time.

The present invention has been made in view of the above-mentioned conventional drawbacks, and it is an object of the present invention to provide a power amplifier device which significantly reduces notching distortion and is suitable for use in semiconductor integrated circuits.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A power amplification device according to the present invention will be described below based on an embodiment thereof with reference to the drawings.

The notching distortion observed in the output waveform of the conventional power amplifier described above is caused by the notching distortion of the composite PNP transistor 14.
-15, 14'-15' The time required to charge the parasitic capacitance of the emitter-base junction is
This is caused by a turn-off delay time, so if charge is accumulated in the parasitic capacitance of the emitter-base junctions of transistors 14, 15, 14' and 15' in advance, this turn-on delay time can be reduced. can. Therefore, a power amplification device consisting of a pair of power amplifiers of the present invention is constructed as shown in Fig. 3, but the same parts as the conventional power amplification device (see Fig. 1) are given the same reference numerals. The difference is that PNP transistors 13 and 1
3' are connected through resistors 16 and 16', and the connection point between resistors 16 and 16' is grounded through diodes 17 and 18.

During operation, the power amplifying device having the above configuration has composite NPN transistors 11-12, 11'-12' and composite PNP transistors 13-14-15, 13'-14'- as in the conventional example (FIG. 1). 15' repeats on and off alternately, and composite NPN transistors 11-12 (composite PNP transistor 13
-14-15) is on or off, the composite
When the NPN transistors 11'-12' (composite PNP transistors 13'-14'-15') are in the off or on state, the input signals of opposite phase and the same amplitude applied to the input terminals 2 and 2' are amplified, and the load resistance Appears at both ends of R _L as output signals with opposite phases and the same amplitude. In this case, the present invention uses a PNP transistor 13 as shown in the figure.
and 13' have resistors 16 and 1
Since the connection point between resistors 16 and 16' is grounded through diodes 17 and 18, transistor 13 is currently on (transistor 13' is on), and transistor 1
Even when transistor 3' is off (transistor 13 is off), transistor 14' (transistor 14)
At the base of is transistor 1, which is on at this time.
4 (transistor 14') base voltage is resistor 1
6 and 16'. As a result, transistors 14', 15' (transistors 14, 1
5) Charge is accumulated in the parasitic capacitance of the emitter-base junction in advance, and the transistor 13' (transistor 13) quickly changes from the off state to the on state, so the above-mentioned notching distortion that occurs in the output waveform at this time is reduced. significantly reduced. Of course, since the connection point between the resistors 16 and 16' is grounded through the diodes 17 and 18, the voltage is slightly lower than the voltage between the base and emitter terminals of the composite transistors 14-15 and 14'-15'. Ori,
Transistors 14 and 15 (transistor 1
When transistors 14' and 15' (transistors 14 and 15') are conductive, transistors 14' and 15' (transistors 14 and 1
5) is sufficiently stable against conduction, rise in ambient temperature, internal heat generation, etc.

As explained above, the power amplifier device of the present invention improves the turn-on delay time of the composite transistor, and as a result, notching distortion can be greatly improved within the audio frequency range, and it is also effective in reducing the distortion rate of the output waveform. It is.

Furthermore, since the power amplifier device of the present invention can be constructed from resistors, diodes, and transistors, it is most suitable for semiconductor integrated circuit implementation.

It goes without saying that even if a resistor (not shown) is substituted for the diode 17 in the embodiment shown in FIG. 3, the same effect as in the above embodiment can be obtained.

As explained above, according to the present invention, it is possible to provide a power amplifying device with great practical value.

[Brief explanation of the drawing]

Fig. 1 is a circuit connection diagram showing a conventional power amplifier, and Fig. 2 is a signal waveform diagram showing the output waveform of the power amplifier shown in Fig. 1. A and A' are power amplifiers 1 and 1'. 3 is a circuit connection diagram showing one embodiment of the power amplifier device according to the present invention. 1, 1'...Power amplifier, 2, 2', 3, 3',
4, 4', 5... terminal, 6, 6', 16, 16'...
...Resistor, 7, 7', 8, 8', 9, 9'...Diode, 10, 10'...Drive transistor, 1
1, 11', 12, 12'...Composite NPN transistor, 13, 13', 14, 14', 15, 15'
...Composite PNP transistor, R _L ...Load resistance.

Claims (1)

[Claims] 1 A transistor of one conductivity type whose collector is connected to one end of the DC power supply and an emitter connected to an output terminal, and a second transistor of the one conductivity type whose collector is connected to the output terminal and the emitter to the other end of the DC power supply a third transistor of another conductivity type, the emitter of which is connected to the output terminal and the collector of which is connected to the base of the second transistor; and an input signal to the bases of each of the first and third transistors. is applied to the first and second amplifiers, the input signal applied to the first amplifier is of a phase opposite to the phase of the input signal applied to the second amplifier, and In a power amplification device that applies each output signal of a second amplifier to both ends of a load to take out the output, the bases of the second transistors of the first and second amplifiers are connected to each other by first and second resistors. connect via
A power amplifying device characterized in that a connection point between the first resistor and the second resistor is connected to the other end of the DC power supply through a forward biased diode.