SU1197052A1 - Power amplifier - Google Patents

Description

The invention relates to radio engineering and can be used in portable electronic equipment with low supply voltage (0),

and also in hearing aids. The collector current of the transistor (T) 1, flowing through the diode (D) 2 and the collector load 3, creates a voltage drop across the D2 - bias voltage (and _сАА ) on one of T 4,5. P) 7, D 6, P8, creates a voltage drop on D6 =

= and _see another T. Συ on D 2.6 opens up T 45 basic-emitter transitions. Even if Σ and <0 _pit , the conditions are created for the normal operation of the phase-reverse cascade. The low-frequency signal currents flowing in collector circuits T 4.5, passing through the base-emitter transitions T9,10, are amplified and create a 12 voltage range in the load,

. close to the maximum possible. (Cpit) · 1 Il.

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The invention relates to radio engineering and can be used in portable electronic equipment with low supply voltage, as well as in hearing aids.

The purpose of the invention is to reduce the minimum allowable voltage of the power source.

The drawing shows a circuit diagram of a power amplifier.

The power amplifier contains an input cascade on the transistor I, a bias circuit on diode 2, a collector load 3, a commercial phase inverter cascade on transistors 4 and 5, a diode 6, resistors 7 and 8, an output two-stroke stage on transistors 9 and 10, a capacitor 11 , load 12 ..

The power amplifier works as follows.

In the initial state, the collector current of transistor I, flowing through diode 2 and collector load 3, creates a voltage drop across diode 2. If diode 2 and transistors 4 and 5 are made, for example, on the basis of silicon, then the magnitude of the voltage drop across diode 2 is equal to the bias voltage on one of these transistors (4 or 5).

The current flowing from the power source along the circuit: resistor 7, diode 6, resistor 8, creates a voltage drop across diode 6 equal to the bias voltage of the other transistor. The sum of the voltages on diodes 2 and 6 provides the opening of the base-emitter transitions of transistors 4 or 5. Thus, even if the supply voltage is lower than the opening voltage of the two base-emitter transitions of transistors 4 and 5, conditions are created for the phase inversion cascade to work properly.

The low frequency signal is fed to the base of the transistor 1, operating in linear mode (mode A),

97052

and from his collector to the bases

transistors 4 and 5.

I

Low frequency signal currents

5 flowing in the collector circuits of the transistors 4 and 5, passing through the base-emitter transitions of the transistors 9 and 10, are amplified and create voltage sweep in the I2 load,

10 close to the maximum possible (0 _piT ). The capacitor 11 is used to separate the constant and variable components of the output signal.

15

Claims (1)

Claim A power amplifier containing series-connected input, intermediate phase-inversion and output 20 push-pull cascades, moreover the output push-pull cascade is made on two transistors connected according to a common emitter circuit and having a different structure; intermediate phase 25 inverse cascade is performed on two transistors connected according to a common emitter circuit and having a different structure, the bases of which are connected | 30 to the collector of the transistor of the input stage, the other to the collector load of this transistor., Included in the scheme with a common emitter, as well as a diode and two resistors, characterized in that, in order to reduce the minimum allowable voltage of the power supply,. bias circuit is formed on one diode forward biased with respect to the collector current of the input stage transistor emitters of transistors intermediate fazoinversnogo cascade connected through another diode reverse-relative emitter currents of these transistors and via respective resistors ^r are connected to the busbars power supply, one bus which is connected to the common bus .