JPS6034284B2 - amplifier circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit having a two-power supply circuit configuration and having a differential amplifier circuit.

Conventionally, various amplifier circuits having differential amplifier circuits have been proposed and put into practical use. If the base bias voltages of the transistors become unbalanced at power-on, which causes a shift in the time at which their transistors are turned on, causing one transistor to conduct before the other immediately after power-on, There is a problem in that the transistor that is turned on ahead of it generates a voltage with a steep rise, which causes shock noise or pop noise.

Therefore, in order to prevent the occurrence of such noise,
It is necessary to balance the base bias voltages of these transistors to be the same at power-up) so that they are simultaneously conductive immediately after power-up. Therefore, it is an object of the present invention to provide a novel amplifier circuit that takes measures to effectively prevent the occurrence of such imbalance.

Embodiments of the present invention will be described below with reference to the drawings.

In the drawings, T and L are the input terminal and output terminal, respectively, and (10) and (1) are the (10) and (1) terminals of the power supply, respectively. 1 is a differential amplifier circuit composed of a first transistor Q, a second transistor Q2, and a third transistor Q3, and the first transistor Q and the second transistor Q2 have their emitters connected to each other. They are connected to each other, and the collector of the third transistor Q is connected to the connection point of their emitters.

The base of the fourth transistor Q4 is connected to the collector of the first transistor Q, and the base of the fourth transistor Q3 is connected to the collector of the first transistor Q.
The base of the fifth transistor Q5 is connected to the emitter of the transistor Q5. These fourth and fifth transistors Q
4 and Q5 are designed to act as drivers for a power amplification circuit constituted by, for example, the sixth and seventh transistors Q and Q7, and as mentioned at the beginning, they are configured according to the conventional circuit configuration. For example, the base bias of these driver transistors becomes unbalanced when the power is turned on, which is one of the causes of noise generation. The emitter of the fourth transistor Q is connected to the power source (
(10) terminal, the emitter of the fifth transistor Q is connected to the (1) terminal of the power supply, and resistors R5 and R are connected to the outer collectors of the fourth and fifth transistors.
6 and the fourth transistor Q
The collector of No. 4 is connected to the base of the sixth transistor Q6, and the collector of the fifth transistor Q5 is connected to the base of the seventh transistor Q7. The sixth and seventh transistors Q6 and Q7 have their emitters connected to each other and their collectors connected to the (10) and (1) terminals of the power supply, respectively. The input terminal T, is connected to the base of the first transistor Q,. Further, the base of the second transistor Q2 is grounded through a series circuit of a resistor R8 and a capacitor C2, and is connected to the emitter connection point of the sixth and seventh transistors Q and Q7 through a resistor R7. The output terminal L is derived from the connection point. second transistor Q
The collector of the first transistor Q is connected to a resistor R and its diode D. are connected to the (10) terminals of the power supply, respectively.

Further, the emitter of the third transistor Q is connected to the (1) terminal of the power supply through a series circuit of a resistor R2 and a diode D2 arranged in the forward direction. The base of the third transistor Q3 is grounded via a resistor R3, and is connected to the (1) terminal of the power supply via a parallel circuit of a diode D3, a capacitor C, and a resistor R4 arranged in the forward direction. ing. Next, the operation of the amplifier circuit according to the embodiment of the present invention described above will be explained.

A signal arriving at the input terminal T is amplified by the differential amplifier circuit 1, and the amplified signal is sent from the collector of the first transistor Q to the base of the fourth transistor Q4. In this case, the fifth transistor Q5 acts as a load resistance for the fourth transistor Q. The output of the fourth transistor Q4 is applied to the bases of the sixth and seventh transistors Q and Q7, thereby causing a push-pull operation across those sixth and seventh transistors, thus The signal from Q is power amplified and taken out from output terminal L. In the operation described above, current from the power supply flows through the diode D, between the collectors and emitters of the first and second transistors Q and Q2 at substantially equal rates.

In this case, the first transistor Q. The magnitude of the sum of the currents flowing through the second transistor Q2 and the third transistor Q2 is determined by the third transistor Q2. In the above-mentioned circuit configuration, the fourth transistor Q4 and the fifth transistor Q are usually used which have the same operating characteristics with only different polarities, and the fifth transistor Q5 is connected to the resistor R.
5 and R6 to act as a constant current source for flowing a constant current. Incidentally, a DC bias voltage to the base of the fourth transistor Q4 is provided by a diode D and a resistor R. now,
Let i be the current flowing through the first transistor Q, and
If the current flowing through transistor Q2 is i2, then (i, + i2) x (diode D
, a voltage v, equal to the internal resistance of , is generated across the resistor R, R,×i. Since a voltage v2 equal to is generated,
The base bias voltage of the fourth transistor Q4 is v, 10v2. Next, considering the fifth transistor Q5, currents i and i2 flow through the series circuit of the resistor K2 and the diode D2. Diode D, and diode D2
If they are the same, their terminal voltages will be equal, and in this case, the terminal voltage of resistor R2 will be (i. i2) x
Since R2, the value of resistor R2 is 1/2 of the value of resistor R.
By selecting R, the terminal voltage of resistor R2 can always be made equal to that of resistor R. Thus, the base voltage of the fourth transistor Q4 and the fifth transistor Q5
The base voltage can be maintained at the same level at all times even when the power is turned on, thereby effectively preventing the occurrence of imbalance as described at the beginning. As can be understood from the above description, according to the present invention, with a very simple configuration, the unbalance problem described at the beginning, which has conventionally been unavoidably encountered in amplifier circuits including differential amplifier circuits, can be solved. It is possible to achieve an excellent effect of being able to solve the problems all at once.

Note that in the embodiment described above, the first to third transistors Q, to Q3 and the fifth and sixth transistors Q5
, Q6 is an NPN transistor, and the fourth and seventh transistors Q4, Q? Since a PNP transistor is used for the first resistor R. is the first transistor Q
, and the second resistor R2 is connected between the emitter of the third transistor Q and the (1) terminal of the power source. The amplifier circuit according to the first to seventh transistors Q. ~Q7
Similar effects can be obtained even if transistors having conductivity types opposite to those described above are used.

In that case, it will be easily understood that what is necessary is to reverse the positive and negative polarities of the power supply terminals and connect the diodes D, to D3 in opposite directions.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an amplifier circuit according to an embodiment of the present invention. T. ...Input terminal, T2...Output terminal, 1
...Differential amplifier circuit, Q. ...First transistor, Q2...Second transistor, Q...
Third transistor, Q...Fourth transistor, Q...
...Fifth transistor, R. ...the first resistance,
R2...Second resistance.

Claims (1)

[Claims] 1. An amplifier circuit having a two-power supply circuit configuration with positive and negative power supply terminals, comprising first, second, and third transistors, the emitters of the first and second transistors being connected to each other, and the emitters of the first and second transistors being connected to each other; a differential amplifier circuit in which the collector of a third transistor is connected to the connection point between the emitters of the first and second transistors; the base is connected to the collector of the first transistor and the positive and negative power supplies; a fourth transistor whose emitter is connected to one of the terminals; a fifth transistor whose base is connected to the emitter of the third transistor and whose emitter is connected to the other of the positive and negative power supply terminals; a voltage drop generating means through which the collectors of the fourth and fifth transistors are connected to each other; and at least two transistors, one of the two transistors being the fourth transistor. In the amplifier circuit, the amplifier circuit includes a single-ended push-pull amplifier circuit, the base of which is connected to the collector of the first transistor, and the base of the other transistor is connected to the collector of the fifth transistor, the collector of the first transistor and one of the power supply terminals. a first resistor connected between the first resistor and the third resistor;
a second resistor connected between the emitter of the transistor and the other power supply terminal, wherein the voltage across the first resistor and the voltage across the second resistor are equal to each other. An amplifier circuit characterized in that the values of the first and second resistors are selected such that.