JPH02174307A - Bias circuit for push-pull amplifier - Google Patents

Abstract

PURPOSE:To reduce current consumption by giving a DC bias current to two transistors (TRs) in series. CONSTITUTION:A current fed from a feeding terminal 3 flows from an emitter to a collector of a TR 11, passes through an output TR 19, a coil 16 and a resistor 14 and flows from the emitter of a TR 10 to the collector and reaches a ground point through an output transformer 19. Thus, the DC bias current flows in series with two TRs 10, 11. Thus, the current is halved with respect to a conventional current. Moreover, the start of winding of the output transformer 19 is selected in this case to cancel the magnetic flux due to a DC generated in two windings thereby preventing the magnetic saturation due to the DC.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low distortion amplifier that operates with low power consumption [Prior Art] In Fig. 2, a conventional push-pull amplifier is shown. Input terminal, 2 is output terminal, 3 is power supply terminal, 4.5
．． 12.13 is a capacitor, 6,7°8, 9.14.1
5 is a resistor, 10.11 is a transistor, 18 is an input transformer, and 19 is an output transformer.

As shown in FIG. 2, the conventional push-pull amplifier connects the collectors of transistors 10 and 11 to both ends of the winding of a transformer 19, respectively, and connects the center tap of the winding of the transformer 19 to ground. 11 receives power through resistors 14 and 15 to their emitters, respectively.

[Problem to be solved by the invention]

In order to use the above-described conventional push-pull amplifier with good distortion characteristics, it is necessary to allow a sufficient collector current to flow through the transistor, resulting in a drawback of high current consumption.

An object of the present invention is to provide a push-pull amplifier bias circuit that solves the above problems.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In the figure, the present invention is a push-pull amplifier using an output transformer 19 with three turns of winding, in which the collector of the first transistor 10 is connected to the first terminal of the first winding of said transformer 19; The emitter of the first transistor 10 is connected to the first terminal of the second winding of the transformer 19 via the first resistor 14 and the coil 16, and the collector of the second transistor 11 is connected to the first terminal of the second winding of the transformer 19. 2
is connected to the second terminal of the winding of the second transistor 11
The emitter of the transformer 19 is connected to the power supply terminal 3 via the second resistor 15, the second terminal of the first winding of the transformer 19 is grounded, and the first terminal of the second winding of the transformer 19 is grounded. The terminal is grounded via a capacitor 17. The rest of the structure is the same as the conventional one shown in FIG.

The current supplied from the power supply terminal 3 flows from the emitter to the collector of the transistor 11, passes through the output transformer 19, passes through the output transformer 19, passes through the resistor 14, and passes through the transistor 10.
flows from the emitter to the collector, passes through the output transformer 19, and reaches the ground point.

As a result, the DC bias current flows through the two transistors 1
0.11 flows in series, the current can be halved compared to the conventional one. Also, at this time, by selecting the beginning of the winding of the output transformer 19 as shown in FIG. 1, the magnetic fluxes due to the direct current generated in the two windings cancel each other out, thereby preventing magnetic saturation due to the direct current.

〔Effect of the invention〕

As explained above, the present invention has the effect of reducing power consumption by halving the bias current.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a Bushgur amplifier bias circuit according to the present invention, and FIG. 2 is a circuit diagram showing a conventional Bushgur amplifier. 1...Input terminal 2...Output terminal 3...
Power supply terminal 4, 5.12.13.17... Capacitor 6, 7.8
．． 9.14.15...Resistor 10, 11...Transistor 16...Coil 19...Output transformer 18...Input transformer

Claims (1)

[Claims] (1) In a push-pull amplifier using an output transformer having a three-turn winding, the collector of the first transistor is connected to the first terminal of the first winding of the transformer, and the emitter of the first transistor is connected to the first terminal of the first winding of the transformer. A first terminal of a second winding of the transformer is connected to a first terminal of a second winding of the transformer through a first resistor and a coil;
connecting the emitter of the second transistor to the power supply terminal via a second resistor, and grounding the second terminal of the first winding of the transformer; A push-pull amplifier bias circuit characterized in that the first terminal of the second winding of the transformer is grounded via a capacitor.