JPS6032419A - Power amplifier - Google Patents

Abstract

PURPOSE:To prevent the unbalancing of the distortion factor between output signals from being caused by applying an output of a parallel negative feedback amplifier to the 1st and 2nd negative feedback power amplifiers so as to give an output of both power amplifiers to a load. CONSTITUTION:An input signal fed from a signal source SG is outputted to its output terminal 2 via the parallel negative feedback amplifier A and fed to an input terminal of the negative power amplifiers AMP1, AMP2. Further, each output signal of the AMP1, AMP2 is outputted as a synthesis signal among a fundamental signal from a signal source SG, a distortion component generated by the parallel feedback amplifier A and a distortion component generated from the AMP1, AMP2. Since the distortion generated in the AMP1, AMP2 is nearly equal, no unbalance of the distortion factor is produced between the output signals of the AMP1, AMP2. Further, the input impedance of the amplifier A is sufficiently large and the decrease in the input impedance viewed from the input terminal is not produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a power amplifier device that uses a pair of power amplifiers to supply an output to one load.

Generally, a BT circuit is a circuit configured to supply an output to one load using a pair of direct-coupled power amplifiers with no output voltage.
, L (balanced transformerless (BALA,
NCED,'lAN8FORME)tLE8s)
) circuit, and conventional examples thereof are shown in FIGS. 1 and 2.

In Fig. 1, AMP1 is an in-phase f+feedback pp1f4 power amplifier, AMP2 is an anti-phase negative feedback power amplifier, and Rgl
+lLg2 and R1-R5 are resistors, KL valve dog (speaker), C1 to C4 are capacitors, 1 input terminal, v
CC indicates W, a pressure source, and 8G indicates a signal generator.

In FIG. 1, the input coefficient to AMPl is directly supplied through a signal generator 8 (supplied from J, the input signal of AMP2 is the output signal of AA+P1 through a resistor) 15, and a resistor divider R6. Here, the output signal of AMPl is output as a composite signal of the fundamental signal from the signal source 8G and the distortion component generated by AMPI, and the output signal of AMP2 is a composite signal of the fundamental signal from the signal source 8G and AMl'l, 2 It is output as a composite signal with the distortion components generated in each.

For this reason, the distortion rate of the output signal of AMP2 causes a problem that the distortion rate is unbalanced between the respective output signals of AΔ4P1. Next, the input impedance Zip when looking inside the circuit from input terminal 1 is shown by equation (1)! do.

Totoru. Therefore, Zio is the input impedance of AMPI, π is pi, f is the frequency, and ■mo is the formula (2) %
Formula % In formula (2), C5 is resistance rtB, R9, 几1
1), (2) with the AC signal bypass capacitor at the intersection of 0
Since the first term on the right side of the equation (2) is sufficiently smaller than the second term (10), the value of the equation (2) is set by the resistance value of JO. Furthermore, in equation (1), Zio is the input impedance of the common-mode negative feedback power amplifier AMPI, so it is sufficiently larger than R. As a result, Zi shown in equation 0) can be set approximately at the resistance value of R, that is, the resistance value of the resistor RIO. To be specific, R8=10Ω, R9=10kn, C3=47
4F, f=1kHz, R1o=50kO, and Zi
o = 5MO tort, R = 50.0003X103 in 50X103 in RIO and 71, Zi =49.5X
103103=.

Next, FIG. 2 shows another conventional example. In Figure 2, AMP
I is a synchronous negative feedback N1 power amplifier, AMP2 is an anti-phase negative feedback power amplifier, Rg, R1-R9 are resistors, and the load (
speaker), C1 to C5 capacitor, 1 is input terminal, V
CC indicates a voltage source, and SG indicates a signal generator.

In Fig. 2, the input signals of AMPI and AMP2 are directly supplied from SG, so the output signals of each of AMPI and AMP2 are the basic signal from 8G and AMPl, AMP.
A composite signal of the distortion components generated in each of the two is output.

Here, when AMP1 and AMP2 are configured with the same circuit, the distortion components generated in each of AMPI and AMP2 are approximately the same. Therefore, AMPI.

There is no problem of distortion rate imbalance between the output signals of the AMP2. Next, the input impedance Zi1 when looking inside the circuit from the input terminal 1 is expressed by equation (3).R in equation (3) is expressed by equation (4).

Here, Zio is the input impedance of the in-phase Koma feedback power amplification section and AMP1, π is pi, and f is the frequency.

However, from the input terminal 1, there is a reverse phase dog feedback weight, and the force amplifier AMP
The impedance when looking at AMP2 is small because AMP2 is in reverse phase, so the impedance when looking at AMP2 from input terminal 1 is equal to R3
Seven. Therefore, equation (3) is derived.

The right-hand side of equation (4) is equivalent to the right-hand side of equation (2), so the first
As explained in the figure, it becomes RIO during R. In equation (3), Zio is the input impedance of the in-phase negative feedback power amplifier AMP1, so it is sufficiently larger than R (middle JO), 143. Therefore, Zi' shown in formula (3) is R
(middle R10) and R3 are set by the parallel resistance value, but R3
Generally, the resistance value is from several hundred ohms to several ohms, so the input impedance Zix seen from input terminal 1 is dominated by the resistance value of 几3, and the first input impedance Z
There is a problem that the input impedance Zix (in a specific example, 21', Ω) is lower than Zix (in a specific example, 50Ω). Speaking communally, I is also 8=10
to Ω, ■ also 9=10 to Ω, ■+, 10=50 to Ω, C3
=47μF, f=1kHz, R3=21cO, Zi.

If ==5MΩ, H-50,0003X103=R1
0, Zi'=1.92X103, which becomes R3.

Therefore, one might think that the resistance value of the resistor l'L3 should not be increased, but it is set to several Ω to several Ω because the resistance value is less than the resistance value of the resistor R3. In other words, the 11fI voltage gain Ay of the negative feedback '11i force amplifier AMP2 of opposite phase is:
If the aperture pressure gain is large enough, generally Av = R4
/I(, 3. Therefore, once the threshold voltage gain is determined, if you increase the resistance value of 11.3, you will inevitably have to increase the resistance value of I(4). .Furthermore, the resistance value of resistor R7 must be made equally large.The reason is that resistor R7 is generally used as Ih of resistor R4 in order to stabilize the DC bias voltage of the e and e input terminals of AMP2.
This is because it is set to the same value as the resistance value. In this way, if the resistance values of the resistors R4, R, and 7 connected to AMP2 increase, the resistance value of the resistor 1'L connected to AMP1 increases.
2. Due to imbalance with JO resistance value! J, A.M.P.
There is a difference in DC bias pressure at the input terminals of AMP1 and AMP2, which causes a DC voltage difference between the output terminals of AMP1 and AMP2. As a result, loads R, L (speaker)
DC current flows through the device, causing problems such as burnout of the load (speaker). In addition, when integrated circuits are formed, disadvantages such as increase in pellet area due to a large increase in resistance value and cost increase occur. Therefore, as described above, the resistance value of the resistor R3 is generally set to several hundred ohms to several ohms.

As described above, in the conventional example shown in FIG. 1, there is an imbalance in the φ ratio between the outputs of AMP1 and AMP2, and in the second case, the problem of a decrease in input impedance occurs. Shi-mau.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power amplifier with a 4% B, T, and L circuit, which prevents unbalance of distortion and decrease of input impedance.

The present invention is characterized in that an input signal is supplied to a pair of amplifiers via parallel negative feedback type amplifiers.

FIG. 3 shows an embodiment of the present invention. In the third part 1,
AMPI is an in-phase negative feedback power amplifier, AMP2 is an anti-phase negative feedback power amplifier, A is a parallel negative feedback amplifier, C1 to C4.
is a transistor, kLg, 1 is also 1-JLti is a resistor,
RL load (speaker), 01 to C5 are capacitors, v
CC is a voltage source, 1 is an input terminal, 2 is a parallel negative feedback amplifier A
SG is a signal generator, and Is, 12 is a constant current source. The input signal supplied from the signal source SG is
is outputted to its output terminal 2 via the parallel negative feedback amplifier A, and at the same time, AMP1.

Applied to the input terminal of AMP2. Therefore, AMPl.

Applied to the input terminal of AMP2. Therefore, AMPI.

The output signal of each AMP2 is the base signal from the signal source SG, the distortion component generated by the parallel negative feedback amplifier A, and AMP1,
A composite signal with distortion components generated in each of AMP2 is output. In other words, the output signal of AMPI, the fundamental signal of signal source SG, the distortion component generated by parallel negative feedback amplifier A, and AMP
The output signal of AMP2 is a combination of the distortion components generated in I, and the output signal of AMP2 is parallel to the fundamental signal of signal source 8G.
This is a composite signal of the distortion component generated in AJ'11P2 and the distortion component generated in AJ'11P2. Here, Amu tithe 1. If AMP2 is the same circuit 41), if it is formed or ζ, then A%1. Pl,
Since the distortion components generated in AMP2 are equivalent to #宕锕, there is no problem of unbalanced distortion rates between the output numbers of AMP l and AMP2.

Next, look at the inside of the input h'i'z from the item 1 of the spacer 1 and calculate the impedance Z i 21'4 using the formula (5).

R in formula (5) is represented by formula (6).

Therefore, Zioz is the input impedance of the parallel negative feedback amplifier A, π multiplied by pi, and f is the frequency.

Since Zioz is the input impedance of the parallel negative feedback amplifier A, it is sufficiently large, more than the general several MΩ, and Zioz
Naka Zio ToiA-Rahr. Yotte, (5) above,
The formula (6) is the same as the formula (1> and (2) above),
As explained with reference to FIG. 1, the input impedance Zi2 can be set by the resistance value of the resistor RIO, and the problem of being below the input impedance as shown in FIG. 2 does not occur.

Next, FIG. 4 shows another embodiment of the present invention. In Fig. 4, AMPI is an in-phase negative feedback power amplifier, AMP2 is an anti-phase negative feedback power amplifier, A is a 1f/outer valve feedback amplifier, and C is an in-phase negative feedback power amplifier.
1 to C16 are transistors, R1 to R16 are resistors, It
,]- is a valve load (speaker), D1~])fi is a diode, C1~C5 is a capacitor, J3 and 14 are constant current sources,
vCC represents a voltage source, and 1 represents an input terminal.

In FIG. 4, as in FIG. 3, the input signal is passed from the input terminal 1 to the in-phase negative feedback power amplifier A
Since R4P t is simultaneously input to the input terminal of the anti-phase negative feedback power amplifier AMP2, there are problems such as distortion rate imbalance between the output signals at the output terminals of each of AMP1 and AMP2, and input terminal 1. The problem of a drop in input impedance when looking inside the circuit does not occur.

,I',j As above, using the B, T, L configuration circuit of the present invention ('r, Therefore, using a pair of power amplifiers in the W-raider technique, the Z, B, T, L circuit is It is possible to prevent problems such as unbalance of distortion rate between each pulling signal and a decrease in input impedance.

Figures 1 and 2 are circuit diagrams showing conventional examples, and Figures 3 and 4 are circuit diagrams showing embodiments of the present invention.

AMPI・・・In-phase negative feedback power amplifier, AM
l) 2...f of opposite phase] Return 3! ) Power amplifier, A.
...Parallel valve feedback amplifier, 1...Input terminal, 2...Output terminal to Q1-Q16...
...Tofunjita, Di~jJ6...Guide, C1~(25...Capacitor, ■Mog, Rg
l, l also g2 flood”~J6...Rei 17fi, IL
L... Negative view I (speaker), 11-14...
... Constant current sweat, ~CC... Voltage source, 8G.
...The signal generation results are indicated by t+.

−・ , ゛, Agent Patent Attorney Shinsu Uchihara,'””,',,,1
Yu Figure 1 Figure 87

Claims (1)

[Claims] The input of the parallel negative feedback type amplifier is used as a signal input terminal, and the output of the parallel negative feedback type amplifier is supplied to a first valve feedback power amplifier as an in-phase amplifier and a second negative feedback power amplifier as an anti-phase amplifier, respectively. , a power amplifier characterized in that a load is connected between the output terminals of the first and second power amplifiers.