The working principle of the public amplifier, the working principle of the power amplifier circuit

If you want to talk about the whole principle, that's a lot.

I can only talk about it in general terms.

Let's start on the left.

Needless to say, those capacitors are all used for coupling, and the three capacitors are used to make it easy for the three signals to pass.

Q1 and the K-level resistors on the left form a bias circuit, this circuit looks simple, but it is more analyzed, 12K and VR1 provide bias current to Q2.

The following 15K is the one that provides bias current to Q3.

Q2 and Q3 are used for driving the rear stage, and the two 20 ohm resistors are used to generate a little voltage between the E poles of the two transistors of the output, which can be used as a bias for the rear stage, so that the working point of the rear stage is slightly higher than that of the AB power amplifier to improve the crossover distortion.

The back triode is the output pole, as the output of current amplification, the middle of the Euro resistance is for several outputs for current balance, without these resistors, it may lead to the output of one of the transistors current too large, the other does not have much current output.

That 30 ohm resistor and capacitor is a Rubert network, and the purpose is to make the horn more like a resistor to the output than an inductor, which is a good thing for the circuit.

That's all there is to say, but this circuit is not a very good amplifier.

First of all, none of the 8 transistors in the output stage have a B-pole resistor, which will make the output current unbalanced.

The circuit has no negative feedback, and an amplifier circuit without negative feedback cannot be regarded as a good power amplifier.

The internal circuit composition, principle and maintenance of the power amplifier, the role of each part of the circuit, and the maintenance precautions.

Mainly use the current amplification principle of the triode to work, simply put, a triode has a base B, collector C, emitter E, when the current of the base B changes slightly, then the current flowing from the collector C to the emitter will change greatly, the current of the collector to the emitter divided by the current of the base is called the amplification factor, or magnification. According to this principle, if one wants to amplify the power, as long as the signal to be amplified is placed at the base, then an amplified signal will be generated at the collector and emitter, of course, the amplification circuit is not so simple, I just talked about a principle, and I am not good at learning electronics. Hope it helps.

The power amplifier can restore the sound of the CD very well, how to do it? Today is a long time to see.

Pure post-stage OCL power amplifier. The input is connected to the push stage or pushed with a 20W IC power amplifier. The 1555 is a bias voltage regulator (similar to a voltage regulator circuit) for the final stage, which provides quiescent operating current to the rear stage and eliminates the crossover distortion caused by the on-voltage of the transistor in the case of small signals.

The post-amp is the normal OCL counter parallel output stage. Input sine wave, the first half of the cycle makes Q2 turn on the work output of large current, the second half of the week makes Q3 turn on the work output of high current, and the rotation work output synthesized amplified power of the sine wave. The input stage capacitor is the front and rear stage isolation capacitance.

In fact, as long as the tube withstand voltage is enough, the working voltage higher than the previous stage can be used (the tube in the figure can use +-50V voltage), not only the output load capacity is enhanced, but the power will be greater. The last current in the figure is that it should be a Class A amplifier, and multiple pairs of tubes are used to balance the large power loss of the Class A power amplifier.

An amplifier balancing potentiometer consists of a resistive body and a rotating or sliding system. When a voltage is added between the two fixed contacts of the resistor body, the position of the contact on the resistor body is changed by rotating or sliding the system, and a voltage that has a certain relationship with the position of the moving contact can be obtained between the moving contact and the fixed contact.

It is mostly used as a voltage divider, where the potentiometer is a four-terminal element. The potentiometer is basically a sliding rheostat, there are several styles, generally used in the speaker volume switch and laser head power adjustment, the potentiometer is an adjustable electronic component.

The balance potentiometer is a coaxial duplex potentiometer, one end of the potentiometer is connected to the front output, one end is connected to the ground, and the center is connected to the power amplifier input. If any of the groups are removed, the channel will be silent. If you don't have the right components to replace, you can connect the two sets of signals directly with separate wires.

The method is: find two bare wires, and wrap the center of the potentiometer and the signal end on the side directly together, note that the center of the potentiometer cannot be connected to the ground at the other end. In this way, both channels have sound.

Class A power amplifier (Class A): refers to the whole cycle of the signal (plus or minus two and a half cycles of the sine wave), Class B power amplifier (Class B): refers to the positive and negative two and a half cycles of the audio signal by two (or two groups) of the push-pull output stage of the power tube in turn to amplify the output of a class of amplifiers, and the on-time of each power tube is half a cycle of the signal.

Class A and B power amplifier (Class AB): between Class A and Class B, the on-time of each power tube of push-pull amplification is greater than half a cycle of the signal and less than one cycle, so that the transition of the two power tubes taking turns to amplify is smooth, and the crossover distortion problem of Class B amplifier is effectively solved, and the efficiency is higher than that of Class A amplifier, so it has been widely used. Unlike the Class A, B, or AB amplifiers described above, Class D amplifiers operate on the principle of switching transistors and can be fully turned on or completely shut off in a very short time of attitude.

The two transistors do not turn on at the same time, so very little heat is generated.