av2030 AVIC, av2030 Datasheet - Page 10

• Manufacturer Part Number: av2030
• Description: Linear Integrated Circuit
• Manufacturer: AVIC

@vic
MUSICAL INSTRUMENTS AMPLIFIERS
Another important field of application for active system is music.
In this area the use of several medium power amplifiers is more convenient than a single high power amplifier, and it
is also more reliable. A typical example(see Fig. 21) consist of four amplifiers each driving a low-cost, 12 inch
loudspeaker. This application can supply 80 to 160W rms.
TRANSIENT INTER-MODULATION DISTORTION(TIM)
When a feedback amplifier receives an input signal which rises very steeply, i.e. contains high-frequency
components, the feedback can arrive too late so that the amplifiers overloads and a burst of inter-modulation
distortion will be produced as in Fig.22.Since transients occur frequently in music this obviously a problem for the
designed of audio amplifiers. Unfortunately, heavy negative feedback is frequency used to reduce the total harmonic
distortion of an amplifier, which tends to aggravate the transient inter-modulation(TIM situation.)The best known
method for the measurement of TIM consists of feeding sine waves superimposed onto square wavers, into the
amplifier under test. The output spectrum is then examined using a spectrum analyzer and compared to the input.
This method suffers from serious disadvantages: the accuracy is limited, the measurement is a tatter delicate
operation and an expensive spectrum analyzer is essential. A new approach (see Technical Note 143(Applied by
SGS to monolithic amplifiers measurement is fast cheap, it requires nothing more sophisticated than an
oscilloscope-and sensitive-and it can be used down to the values as low as 0.002% in high power amplifiers.
wave-form. The amplifier has no difficulty following the slow ramp but it cannot follow the fast edge. The output will
follow the upper line in Fig.23 cutting of the shade area and thus increasing the mean level. If this output signal is
filtered to remove the saw-tooth, direct voltage remains which indicates the amount of TIM distortion, although it is
difficult to measure because it is indistinguishable from the DC offset of the amplifier. This problem is neatly avoided
in the IS-TIM method by periodically inverting the saw-tooth wave-form at a low audio frequency as shown in
Fig.24.Inthe case of the saw-tooth in Fig. 25 the means level was increased by the TIM distortion, for a saw-tooth in
the other direction the opposite is true.
Transient inter-modulation distortion is an unfortunate phenomena associated with negative-feedback amplifiers.
The "inverting-sawtooth" method of measurement is based on the response of an amplifier to a 20KHz saw-tooth
AV2030
Fig.21 High power active box for musical
instrument
20 to 40W
20 to 40W
20 to 40W
20 to 40W
Amplifier
Amplifier
Amplifier
Amplifier
LINEAR INTEGRATED CIRCUIT
INPUT
V1
V1
V2
V3
V4
AMPLIFIER
PRE
Fig.22 Overshoot phenomenon in
V2
Å
feedback amplifiers
V4
V3
FEEDBACK
AMPLIFIER
POWER
PATH
V4
OUTPUT
QW-R107-004,B