BTL∗1 output type is designed and evaluated on the assumption that it is used with BTL system. If it is used with SE∗2 output, not only that the electrical characteristics described in the datasheet will not be obtained, but also pop noise may occur due to the absence of a built-in pop noise prevention circuit for SE output. That is why this not recommended.
BTL∗1 Abbreviation for Bridged Tied Load, also called Balanced Transformer Less. By bridging the outputs of the two amplifiers and connecting them to the loudspeaker, the output voltage is doubled and the output power is quadrupled compared to the SE output type.
SE∗2 Abbreviation for Single Ended. A method in which a Speaker is connected between the Speaker Amplifier output and GND. Since the Speaker Amplifier output is biased by half (1/2) of the Power Supply Voltage, a coupling capacitor must be placed between the Speaker Amplifier output and the Speaker to prevent DC current from flowing through the Speaker. Since the load resistance of the Speaker is generally low (4~8Ω), a large coupling capacitor of about 1000µF is needed to pass low frequency range.
Class-AB Speaker Amplifiers, also called Linear Amplifiers, are Speaker Amplifiers that amplify the input signal as it is to drive the speaker. Generally, this method has an efficiency of less than 50% and generates a lot of heat. Class-D Speaker Amplifiers, also called Digital Amplifiers, are Speaker Amplifiers that convert (analog) input signals into pulses as output. This method achieves high efficiency and low power consumption by converting the output into PWM∗1 pulses.
PWM∗1 Abbreviation for Pulse Width Modulation. In the case of a class-D Speaker Amplifier, an LPF (low-pass filter) is attached to the output so that the carrier signal is removed and the audio signal can be extracted.
Class-D Speaker Amplifiers have higher efficiency and lower power consumption than that of Class-AB Speaker Amplifiers, resulting in less heat generation. However Class-D Speaker Amplifiers have the disadvantage of requiring more external components because an LC filter is generally inserted at the output terminal to eliminate the carrier frequency of PWM. For small output Speaker Amplifiers of around 2 W, it is recommended to use class-D Speaker Amplifier if low power consumption is important. On the otherhand, if reduction of external components is important then class-AB Speaker Amplifier is recommended. For Speaker Amplifiers with medium or higher output power, such as those with output power exceeding 5 W, the Class-AB Speaker Amplifiers may require a heat sink for heat dissipation, which may not reduce the mounting area. Also, since Class-AB Speaker Amplifiers with a linear drive system have better EMI∗1 characteristics than Class-D amplifiers with a pulse drive system, this point should also be taken into consideration when making a selection.
EMI∗1 Abbreviation for Electro Magnetic Interference. Electromagnetic interference is when radio waves or high-frequency electromagnetic waves affect electronic equipment as noise. EMC is also referred to as Electro Magnetic Susceptibility (EMS), which is the ability not to be disturbed by electromagnetic interference.
The Class D speaker amp's drive output stage utilizes high efficiency PWM drive (H or L) based on the output signal level. This results in low power loss and high efficiency (85-90%).In contrast, conventional analog amps feature Class AB output, requiring (among other things) a bias current. The result is low efficiency and high heat generation, requiring an external heat sink.
Besides high efficiency and low heat generation, ROHM Class D speaker amps provide a number of advantages: 1.High fidelity (low noise, low distortion) 2.Popping noise eliminated (via soft mute function) 3.Multiple protection functions built in (preventing IC/speaker damage)
Based on the application a simple filter (i.e. ferrite beads, ceramic capacitor) can be used. For example, active speakers used for compact LCDs or iPod docks are products that use short speaker cables, while large-screen LCDs require longer speaker cables, resulting in the generation of unwanted radiation (EMI) requiring countermeasures (i.e. filters).
Of course. Speaker output power is determined by VCC (supply voltage) and the speaker load (in ohms). 20W output results from a supply voltage of 18V and a speaker load of 8Ω. For 10W output the conditions are: 13V VCC and 8Ω speaker load.
It is the abbreviation of Bridge Tied Load. It reverses the speaker both terminals to connect by using two amplifier circuits compared with a usual single amplifier. If without output coupling capacitor,it may has an advantage that output electric power quadruples.