If pure tone signal was applied to the input of an amplifier, we would (upon measurement with special test equipment) find that the output signal of the amplifier was no longer pure. A pure tone (sinewave) signal has no harmonics it consists of only one single frequency. Harmonics of a signal are signals which are related to the original (or fundamental) by an integer (non decimal) number. One common type of distortion is harmonic distortion. Noise can be considered a type of distortion. These undesirable characteristics are lumped together and called distortion. All amplifiers alter input signals, generally in two ways: they make them stronger (amplify) them, and they add characteristics which did not exist in the original signal.
The frequency - phase characteristic summarizes frequency and phase characteristics of the amplifier in the field of a range of reproduced frequencies. The frequency characteristics determines relation of a gain of amplifier to frequency phase characteristics the phase shift of an output signal on relation to input signal (in frequency function of an input signal). The ratio usually expresses in decibels and represents (in a theoretical case) a linear function. The dinamic range determines a ratio between maximum output and input tension of the amplifier. The power frequency bandwidt is an interval of frequencies within the limits of which at the certain factor of distortions k, output power changes no more, than on ☓ dB in relation to output power on frequency in 1 KHz. The frequency bandwidt at gain equal to unit is an interval of frequencies on which borders the gain values equal to unit. Instead of a frequency bandwidt, sometimes defined a frequency bandwidt at gain equal to unit or a power frequency bandwidt.
In the certain cases when the manufacturer wants to emphasize the expanded range of working frequencies of the amplifier at the improved non-uniformity frequency characteristics, the size of non-uniformity (1 dB, 0,5 dB etc.) is indicated also. The frequency bandwidt Bw - area of frequencies (a bandwidt from bottom limit frequency Fl up to top frequency Fh) within the gain changes no more than on ☓ dB, concerning gain measured on frequency 1 KHz. The gain depends on value of external components, from resistance of loading Rl, input resistance Rin, a supply voltage Vcc, frequency and temperature. The gain Gv can be expressed as a direct ratio (V/mV or V/µV), and in the logarithmic relation (in decibels -dB). The gain Gv (on a current, a voltage or power, depending on purpose of the amplifier) represents the logarithm of the ratio of signal output from a amplifier to signal input to the amplifier.
Main of parameters used for the description of power audio amplifiers is following: a gain a bandwidt a dynamic (phase, phase-frequency, peak (amplitude)) characteristic linear and nonlinear distortions efficiency input characteristics (impedance, current, voltage and power, impedance of a source of an input sound signal) output characteristics (impedance, current, voltage, output power) a dinamic range signalto-noise ratio and maximum ratings of electrical parameters. In the literature, the great many of the characteristics which one describe the electrical and operational parameters of power audio amplifiers depending on evaluation yardsticks and can give completely different estimations to quality of operation of a amplifiers. For correct usage of integrated circuits of the power audio amplifiers, irresepective of a field of application, it is necessary to know following: - Function of integrated circuit - The main electrical characteristics - Schematic of connection and (or) internal structure - Package type - Equivalents (replacements).
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With reference to consumer and professional electronics equipments, the greatest popularity are the integrated circuits-power audio amplifiers, due to their advantages - schematic simplicity, small dimensionss, large range of output powers, polyfunctionality. INTRODUCTION One of the basic components of any sound-reproducing system, without dependence from its class is the power amplifier of audio frequencies called also the power audio amplifier. SMD marking codes for power audio amplifiers in SMD cases Logos, contact info and web-adresses of integrated circuits powe raudio amplifiers manufacturers Power audio amplifiers schematics of connections 5000 Inte grated Cir cuitsInteg Circuitspo wer audio amplif ier s pow amplifier iers databook Introduction
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