JPS5986317A - complementary amplifier - Google Patents

Abstract

PURPOSE:To suppress the power consumption at no signal and to supply sufficiently a drive current by detecting an output of a power amplifier and driving sufficiently transistors (TRs) of complementary connection of the power amplifier. CONSTITUTION:A differential amplifier circuit comprising TRsQ13, Q14 is balanced at no signal. A value of I2+I4/2(I2, I4 are currents of constant current sources I2, I4) flows to diodes Q7, Q8 connected in series. In inputting a negative half cycle to an input terminal of a voltage amplifier section, the base potential of the TRQ14 is decreased and the current I4 flows through the TRQ14 to ground. Thus, an output signal of a TRQ5 drives a TRQ12 of the power amplifier as it is. In inputing a positive half cycle signal to the terminal IN, since the base poetential of the TRQ14 is increased, a collector current of the TRQ13 is increased. Thus, a TRQ6 increases the collector current and supplies a sufficient drive current to a TRQ10 of the power amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a complementary amplifier, and more particularly to an improvement in a bias circuit that drives a power amplification stage thereof.

[Technical background of the invention]

Traditionally, complementary amplifiers have a power increase of +1c4 stages'1
By operating in the Z13 class, it is possible to reduce the power consumption when there is no signal while maintaining good characteristics, and it is becoming more popular as it is integrated into ICs.

Such a complementary amplifier includes, for example, a differential amplification circuit including transistors Ql and Q2, a current mirror circuit including transistors Q3 and Q4, an amplification transistor Q5, and constant current sources Il and I2 as shown in FIG. (A voltage amplifying section is configured. A pace bias is supplied to the pace of the transistor Q1 from which the input terminal IN of the corresponding complementary amplifier is derived by resistors R1, R2, and R3.

The signal output from the midpoint of the connection between the constant current source 2 of the voltage amplifying section and the collector of the transistor Q5 is an inverted output signal with an opposite phase to the signal supplied to the input terminal IN. Transistor Q that makes up the circuit
6 emitters. This transistor Q6 is a diode Q7 which is a transistor commonly connected between the constant current source I3 and the collector pace.
, the pace bias is driven by Q8, and the collector is connected to the diode Q9 and transistor Q of the power amplifier section
The emitter is connected to the input part of a current mirror circuit made up of a diode Q11 and a transistor Q12 of a power amplifying part. These diodes Q and Q+t are each made of a transistor whose collector spaces are commonly connected.

Finally, if the emitter level of transistor Q6 changes in the positive direction, transistor Q12 is driven, and input terminal I
The negative half cycle of the N signal is amplified, and when the emitter level of the transistor Q6 changes in the negative direction, the transistor Q6 is turned on and the transistor Qro is driven, and the positive half cycle of the input terminal IN signal is amplified. The cycle is amplified. As a result, the complementary amplifier shown in Fig. 1 is capable of class B operation, and the output terminal of the power amplification section (that is, the connection midpoint of each collector of the transistor QIOIQ12) can generate 1W without unnecessarily consuming the power provided by the power supply VCO. Load LDf, such as a speaker, connected to
t drive. Further, the output signal of the power amplification section is negatively fed back to the transistor Q2, which serves as the inverting input terminal of the differential width circuit, through a feedback circuit consisting of resistors R41R5 and capacitors C.

[Problems with background technology]

By the way, a complementary amplifier having a bias circuit as shown in Fig. 1 reduces the current of the current source I3 in order to reduce power consumption when there is no signal, or reduces the emitter area of the diodes Q7 and Q8 made of transistors and the transistor Q6. The ratio of the emitter area must be increased.

However, if the current is reduced by 1 or even 1 arc Ia', there is a problem that a sufficient driving current cannot be obtained particularly for the transistor Qlo of the power amplification section. Also, for example, a
a The voltage amplification section and bias circuit of the amplifier in Figure 1 are I
In the case of C, there is a problem that it is difficult to form a transistor with a large emitter area. For this reason, it has been difficult to construct a complementary amplifier that can provide a sufficient drive current for the power amplifying section and that consumes very little power.

[Purpose of the invention]

This invention was made in view of the above points, and it is possible to suppress power consumption when there is no signal, and to supply sufficient drive current to the power amplification section, thereby increasing amplification capacity. The overall objective is to provide a complementary amplifier with good performance.

[Summary of the invention]

The present invention includes a voltage amplifying section, a power amplifying section including at least one pair of complementary transistors 4, and a transistor connected in series with a constant 17 current source and a transistor to which pace bias is supplied by a diode. and a bias circuit for selectively driving the complementary-connected transistors by turning on and off the transistor according to the polarity of the output signal of the 11L pressure amplifying section, and having a class B operation, the power When all the outputs of the amplifier section are detected and the transistors of the bias circuit are turned on, a sufficient pace 'III: bfi is supplied to the transistors so as to sufficiently drive the complementary connected transistors of the power amplifier section. The present invention is characterized in that it is equipped with a differential amplifier circuit.

[Embodiments of the Invention] Hereinafter, a sister example of the present invention will be described in detail with reference to the drawings.

Figure @2 is a circuit diagram showing a complementary amplifier according to the present invention. However, in Figure 2, the same parts as in Figure 1 are given the same reference numerals and their explanations will be omitted.

That is, the bias circuit k is connected to the base of the transistor Q6 and the collector of the PNP type transistor Q+3. The above transistor Q1g is
The pace is connected to the connection midpoint of the resistor R(l R2,
The emitter is connected to the emitter of a PNP type transistor Q+4, and the current is supplied via a constant current source I4.
! has been completed.

The collector of the transistor Q1au is grounded, and the conductor is connected to the midpoint between the collectors of the transistors Q1G1Q12 and the resistor R4.

That is, in the complementary amplifier constructed as described above, the transistor Q13 is activated when there is no signal.
．． The differential amplifier circuit composed of Q14 is in a balanced state, and if the constant current source 4's current is expressed by its sign, the collector currents of the transistors Q131Q14 are 4/2. Therefore, the diode Q connected in series
7, Qll has a current of magnitude I2 + I4/2, 6iL, if the current at Sadaki-ryugen 2 is indicated by its sign.
will flow.

On the other hand, when a negative half-cycle signal is input to the input terminal IN, the output terminal level decreases, so the transistor Q1
The current from the constant current source I4 is connected to ground through the transistor Q14. Therefore, the output signal of the transistor Q5 (that is, the td1 pressure booster width part force signal) is directly transmitted to the transistor Q of the 'nZ force amplifier part.
1□ and drives the transistor Q12.

Furthermore, when a positive half-cycle signal is input to the input terminal IN, the base voltage of the transistor Q14 increases, so the transistor Q14 starts to cut off and the transistor Q14 starts to cut off.
The collector end flow of I3 increases. Therefore, transistor Q13 is connected to transistor Q6's base and diode).
' Since the voltage can be raised to about tk at the midpoint of J and ff of Q7, transistor Q6 increases the collector current Me and supplies sufficient bias current to the transistor Qls in the power amplification section. I can do it. Since the collector current of the transistor Q13 is regulated by the constant value d'A I4, the transistor Q6 is not driven excessively, and the current source I3 is kept constant. Therefore, it is possible to reduce the power consumption of the complementary amplifier in question (i), which is extremely advantageous.

This invention is not limited to the above embodiments (
For example, it can be constructed as shown in FIG. 3 or FIG. 4. However, in FIGS. 3 and 4, the same parts as in FIG. 2 are designated by the same reference numerals (=t) and their explanations will be omitted.

That is, in the case of FIG. 3, the conductor of the transistor Q6 is connected to the midpoint of the connection between the resistors R4 and R5 forming the feedback circuit.
This is a differential amplifier circuit with a reduced offset component.

In the case of FIG. 4, the collector current of the transistor Q1g is applied by 6iU L to a resistor R6 inserted between the cathode side of the diode Q8 and the ground.

In either of the cases of FIG. 3 and FIG. 4, the operation is similar to that of the circuit of FIG. 2, and the same effects can be provided.

It goes without saying that various other modifications and applications are possible without departing from the spirit of the invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to suppress power consumption when there is no signal, and to provide a large amplification capacity by supplying sufficient driving current to the power amplification section. It is possible to provide a good complementary amplifier with

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional complementary amplifier 1hlIi, Fig. 2 is a circuit diagram showing an embodiment of a contimentary amplifier according to the present invention, and Figs. It is a circuit diagram showing an example of a gun. Qr ~ Qs + Qlo + Q12 ~ Qx4-
Transostor, 11~■4...constant current source, Qy
I Qs, Qg 1Qlt...Diode-19, R, ~
R6...Resistance, C...Capacitor, LD...Load.

Claims (1)

[Claims] A voltage amplification section, a power amplification section comprising at least a pair of complementary-connected transistors, and a transistor to which a pace bias is supplied by a constant current source and a diode connected in series; A complementary amplifier that operates in class B and includes a bias circuit that turns on and off the transistor according to the polarity of the output signal of the amplifying section and selectively drives the complementary connected transistors, and detects the output of the power amplifying section. and a differential amplifier circuit configured to supply enough pace current to the transistor in the bias circuit in a state where the transistor is turned on to sufficiently drive the complementary-connected transistors of the power amplifier section. Complementary amplifier with all features.