By talking to Exchange several summary of current power amplifier

Current amplification circuits commonly there are several:

First: the Horn following some resistance to current sampling, actually feedback back or voltage signal is analog current feedback, who is up to, but this circuit faulty, there are 2 reasons:

1, is his output gain as the impedance changes (speaker impedance increases output amplitude increase) the result of adding the trumpet 2-end is not a constant voltage, (of equal amplitude input) like this can bring to the Horn on power constant.

But don't forget that the speaker sound pressure characteristic curve is in constant pressure output of TEST of Ah, so simple that circuit and bad sense of sound, listen to the poor, the fun, but has improved to the circuit voltage negative feedback, plus a reasonable amount of this type of current is negative feedback, to make good sound can be, but at this point the current role of negative feedback is to change the power amplifier of damping coefficient of amplitude-frequency characteristic little effect on the radio enthusiasts of the "Handbook on the Hi-Fi amplifier," a book is more of this circuit.

2. the sampling points in the Horn of the following, huh, huh, horn is a inductive, current flows through the inductor its phase but will change the Oh, low frequency, high-frequency could shifters 90 degrees.

Oh, phase characteristics.

Second: negative resistance amplifier, in addition to some special occasion, first used on the stereo and success are YAMAHA, its main role is on the low-frequency extension has good improvement, but the frequency above 200Hz would play a deterioration of the quality, the effect is commonly used in low frequency active speakers.

In fact, this circuit is and speakers match, no real use alone. Its working principle is: If the speaker is a rigid body, with a pipe, you can become an ideal Hall Mo Zi resonance box, regardless of the size of this case, the thickness of the pipe, provided that they meet the Hall Mo Zi resonance formula. Even the resonant point 20Hz can also be made to the size of the box, only the efficiency, since the speakers on the trumpet, the Horn when the sound is in movement, the speaker is not a rigid body, then the box will not produce Hall Mo Zi.

Therefore, if the sound of the trumpet of the diaphragm is stationary.

Then, close the box, you can meet the rigid body Hall Mo Zi resonance conditions, can be arbitrary design this box of resonance point. Audible when the speaker is not moving job is negative resistance power amplifier to the task. Negative resistance power amplifier works is when the Horn in lower frequency bands work its impedance characteristics of rapidly changing, amplifying circuit through the current sampling will this change out back to the PA, making the amplifier to the current form control Horn, if equivalent to make amplification circuit analysis, you can find power amplifier on the calculation of internal resistance to negative resistance characteristics.

When a dynamic zoom allows Horn with the internal resistance is close to the amplifier.

The results of this circuit allows Horn no matter which direction are subject to strong damping. As long as the voice to end, Horn froze, box becomes rigid. The so-called negative resistance, blunt is the positive feedback. Oh, know why only in low frequency application. In 1995, the radio and TV law on the details. You can go and see

Third: current feedback amplifier modules, this is the practical, current amplification circuit, it is true that current-feedback-feedback, it is the current of the signal, not the voltage, means that a negative feedback-not a plus, but joined with current flows.

This circuit was on video transmission, or the instruments like what's on the oscilloscope uses many.

Due to the low resistance of negative current feedback input this circuit of high frequency characteristics of excellent, capacitive load capacity of the drive, as long as into the too-strong improvement found do power amplifier is very good, you can compensate for voltage amplifier some deficiencies, like low-loop frequency response, closed loop of transient frequency distortion, extremely weak capacitive load drive capability.

The disadvantage is that the open-loop gain circuit is relatively low, closed-loop after distortion than voltage amplifier high an order of magnitude. However, do good total distortion would not have been 0.01%, Oh, you know, Clair power amplifier is current-mode, since the circuit condition relatively new introduction to the article, many find it yourself!

By the way, there is another, called current pour-power amplifier, it works in a power amplifier with 2 amplifier, 1 r, a CPI.

By class a amplifier will current input mode b amplifier output to correct the distortion amplifier, while negative feedback loop where access LC compensation adjustment via precision bridge, total distortion can be 0.

0001% following, exaggerated, once popular over time, however, debugging is too complex, and the required equipment requirements are too high (you can test the 0.0001% distortion-distortion Analyzer are more than 100 million Yuan, hehe), good sound is not easy to do, now playing in person. This can be considered a bar because of the distortion correction is current. Zoomlion had several, now seems to be discontinued.