LM4668MH _ BTL
class-D power audio amplifier with shutdown.
1468 – 3571 – 3572 – 3573 – 8510 –
8515 – 8520 – 8530 - OPA502BM - OPA502SM - OPA511AM - OPA512BM - OPA512SM –
OPA512SM – PA01 - PA10A - PA12 - PA12A - PA12H - PA12M - PA73 - PA73M - TPA12 - TPA12A _ Power operational _audio amplifier.
LM4668LD - LM4680SD _ BTL class-D
power audio amplifier with shutdown.
5G31A - 5G31B - 5G31C _ Power audio
amplifier.
A1034P - AN7108 - CXA1005P - CXA1034M
- CXA1034P - CXA1634M - CXA1634P - KA22132 _ Dual playback preamplifier, volume
control, power audio amplifier for headphone.
5G37 - Power audio amplifier.
BA4918-V12
WHAT IS SENSITIVITY
Sensitivity of the amplifier
understand value of the sine wave input voltage, necessary for obtain of the maximal
output power. Frequently, some manufacturers indicate value of a nominal input
voltage. A nominal input voltage is a sine wave voltage applied to an input of
the amplifier for obtain of nominal output power. It is meant, that the volume
regulator of the amplifier should be exposed on the maximal value. Besides linear and nonlinear distortions, any
real amplifier generates the additional signals. Because of it, on an output of
the amplifier there is a signal distinct from zero, even in absence of an
entrance signal. This signal called as output noise and can be considered as
the sum of infinite number of sine wave voltage (not only harmonious) including
in a sound range of frequencies. Sources of internal noise of the amplifier are
thermal noise of resistors, and also shot, flickering and thermal noise of
active components (transistors and diodes). Quantitatively a value of noise on
an output describe through effective value of noise. As the voltage of
noise grows simultaneously with a range of reproduced frequencies, it is
necessary to specify frequencies within the limits of which measurements of
noise on an output of the amplifier were made. If the range of frequencies is
not underlined, own noise are measured within the limits of a working range of
frequencies of the amplifier. The range
of change of a output voltage is determined by a difference between the maximal
and minimal instant value of a voltage on an output of the amplifier. These
parameters called sometimes a peak output voltage and designate Up-p
(peak-to-peak).
There are many terms used to describe
the amplifier power ratings- the maximal sinusoidal power, maximal continuous
power, RMS power, music power (IHFM), peak power, instantaneous power.
Depending on indicated term for output power, the same amplifier can have value
which one differ in some times. Not resorting to the theories we shall mark
that:
Maximal sinusoidal power- is the power delivered on optimal load (for the given amplifier), at a sine-wave input signal, when THD of the output signal reaches value of 10%.
Maximal continuous power- this same as maximal sinusoidal power and occurs under such name in the datasheets of USA and Japan manufacturers.
RMS power- (Root Mean Square power). In the simplified form is described as the power, giving on optimal load (for the given amplifier), at a sine-wave input signal, when output signal completely limits by an output stage of the amplifier and gains the square shape.
Musical power- IHFM (Institute of High Fidelity Manufactures) is the power delivered on optimal load (for the given amplifier), at a complex (musical) input signal, when THD of the output signal reaches value of 10%. The peak power and instantaneous power describe extreme (critical) operation conditions of the amplifier and are specified basically in the advertising purposes. The impedance of load has optimal value for each amplifier and determines a maximum output current (power) giving by the amplifier. If the impedance of load is less than a optimal value, a output current (accordingly output power) of the amplifier can exceed maximum rating and he can be shattered. If the impedance of load is more than optimal value, the output current (accordingly output power) of the amplifier will be less (under identical conditions of operation) than is specified for the given amplifier. On a connection type of load it is possible to distinguish single ended (SE) and Bridged-Tied Loads (BTL) amplifiers. On a single ended amplifiers the load are connected between an amplifier output and ground (GND). Bridged amplifiers work basically as follows: a single input signal is applied to the amplifier. Internal to the amp, the input signal is split into two signals. One is identical to the original, and the second is inverted (sometimes called phase-flipped). The original signal is sent to one channel of the amp, and the inverted signal is applied to the second channel. Amplification of these two signals occurs just like for any other signal. The output results in two channels which are identical except one channel is the inverse of the other. The load is connected between the two amplifier output terminals. In words, one channel “pulls” one way while the second channel “pulls” in the opposite direction. This allows to deliver (at same load and at same power supply) in 3 times lot of power than at single ended amplifiers. Due to improvements in the speed, power capacity and efficiency of modern semiconductor devices, the class-D amplifiers recently have received broad applying. Class-D amplifiers use a technique called pulse width modulation (sometimes combined with pulse frequency modulation). The input signal is converted to a sequence of pulses whose width at any time is proportional to the amplitude of the signal at that time. The frequency of the pulses is typically thirty or more times the highest frequency of interest in the input signal. The main advantages of a class- D amplifiers are efficiency and simplicity. Efficiencies are in the 80% to 90% range. Because the output pulses have a fixed amplitude, the switching elements (usually MOSFETs) are switched either on or off, rather than operated in linear mode. This means that very little power is dissipated by the transistors except during the very short interval between the on and off states. The wasted power is low because the instantaneous power dissipated in the transistor is the product of voltage and current, and one or the other is almost always close to zero.
Maximal sinusoidal power- is the power delivered on optimal load (for the given amplifier), at a sine-wave input signal, when THD of the output signal reaches value of 10%.
Maximal continuous power- this same as maximal sinusoidal power and occurs under such name in the datasheets of USA and Japan manufacturers.
RMS power- (Root Mean Square power). In the simplified form is described as the power, giving on optimal load (for the given amplifier), at a sine-wave input signal, when output signal completely limits by an output stage of the amplifier and gains the square shape.
Musical power- IHFM (Institute of High Fidelity Manufactures) is the power delivered on optimal load (for the given amplifier), at a complex (musical) input signal, when THD of the output signal reaches value of 10%. The peak power and instantaneous power describe extreme (critical) operation conditions of the amplifier and are specified basically in the advertising purposes. The impedance of load has optimal value for each amplifier and determines a maximum output current (power) giving by the amplifier. If the impedance of load is less than a optimal value, a output current (accordingly output power) of the amplifier can exceed maximum rating and he can be shattered. If the impedance of load is more than optimal value, the output current (accordingly output power) of the amplifier will be less (under identical conditions of operation) than is specified for the given amplifier. On a connection type of load it is possible to distinguish single ended (SE) and Bridged-Tied Loads (BTL) amplifiers. On a single ended amplifiers the load are connected between an amplifier output and ground (GND). Bridged amplifiers work basically as follows: a single input signal is applied to the amplifier. Internal to the amp, the input signal is split into two signals. One is identical to the original, and the second is inverted (sometimes called phase-flipped). The original signal is sent to one channel of the amp, and the inverted signal is applied to the second channel. Amplification of these two signals occurs just like for any other signal. The output results in two channels which are identical except one channel is the inverse of the other. The load is connected between the two amplifier output terminals. In words, one channel “pulls” one way while the second channel “pulls” in the opposite direction. This allows to deliver (at same load and at same power supply) in 3 times lot of power than at single ended amplifiers. Due to improvements in the speed, power capacity and efficiency of modern semiconductor devices, the class-D amplifiers recently have received broad applying. Class-D amplifiers use a technique called pulse width modulation (sometimes combined with pulse frequency modulation). The input signal is converted to a sequence of pulses whose width at any time is proportional to the amplitude of the signal at that time. The frequency of the pulses is typically thirty or more times the highest frequency of interest in the input signal. The main advantages of a class- D amplifiers are efficiency and simplicity. Efficiencies are in the 80% to 90% range. Because the output pulses have a fixed amplitude, the switching elements (usually MOSFETs) are switched either on or off, rather than operated in linear mode. This means that very little power is dissipated by the transistors except during the very short interval between the on and off states. The wasted power is low because the instantaneous power dissipated in the transistor is the product of voltage and current, and one or the other is almost always close to zero.
WHAT IS INTER-MODULATION DISTORTION
It is the second “major” type of
distortion that is often specified for amplifiers. Intermodulation distortion is much more
objectionable to the human ear, because it generates non-harmonically related
“extra” signals which were not present in the original. Basically, two pure
tones are simultaneously applied to the input of the amplifier. If the
amplifier were perfect, the two tones (and only the two tones) would be present
at the amplifier output. In the real world, the amplifier would have some
harmonic distortion (as described above), but careful observation of the output
signal (using laboratory equipment) would reveal that there are a number of new
tones present which cannot be accounted for as a result of harmonic distortion.
These “new” tones are called “beat products” or “sum and difference”
frequencies, and are a result of the interaction of the two pure tones within
the amplifier. No amplifier is perfect,
all have some non linear characteristics. Whenever two signals are applied to a
nonlinear system, new signals (in addition to the original two) are generated.
For a good amplifier, the new signals are very small in relation to the two
original tones. All amplifiers are
generally rated for Total Harmonic Distortion (or THD), usually at full power
output over a given frequency band with a particular load. Good values are
anything less than 0.5 %THD. When an amplifier is measured for THD, a pure tone
is applied to the input and the output is measured with special test equipment.
The energy of the pure tone is measured, and the energy of the harmonics is
measured. Those two values are compared, and a THD rating is calculated. A THD
rating of 1% means that the total energy of all the harmonics combined is one
one-hundredth of the energy in the fundamental. Harmonic distortion (although
certainly undesirable) is one of the more tolerable types of distortion as long
as it is kept reasonably low. Distortion levels of 10% may be very
tolerable. At increase of input signal
In the output voltage, a current and power are increased, but also the factor
of nonlinear distortions simultaneously grows. Therefore, for reduction of
nonlinear distortions target capacity of the amplifier are artificial limit in
comparison with the greatest possible output power.
