What are the key advantages of IC power amplifiers over conventional discrete designs? Three factors stand out: Small Current Loops: With power amplifier ICs, a fully-functional amplifier can be built using merely a handful of capacitors and resistors. This austerity lends itself to a compact layout, with tiny current loop areas compared to discrete designs. Why is the loop area important? The smaller the current loop, the less noise picked up by the circuit. The inside of the amplifier enclosure is actually a noisy place, with lots of high-order harmonics from the power supply (for Class AB amplifiers) and multiples of 60Hz from the transformer floating around. Given such a noisy environment, the small loop area is a great antidote to unwanted noise. The compactness of the IC power amplifier results in a very clean noise floor, well below the realms of audibility. Small Parasitic Capacitances and Inductances: The integrated-circuit technology reduces drastically the capacitances and inductances associated with the layout. Within the IC, wiring distances are orders of magnitude shorter compared to discrete designs. Also, outside the IC, the layout can be compact, as already mentioned. All of this, along with the sound circuit design of LM3886/4870, contributes to superior speed without resorting to expensive technologies. Even with a 2uF capacitor load, just about the worst capacitive load it will drive, the amplifier remains stable and well-behaved. Its excellent transient response is well suited to driving all types of loudspeakers. Close and Fast Thermal Tracking: Another key advantage of IC amplifiers is the close thermal tracking of all the transistors. Since all the transistors are on the same chip, any excessive heating in the output transistors can be detected fast and reliably, and actions can be taken quickly to protect the amplifier and the loudspeaker (See National Semiconductors Application Note AN-898 on SPiKe protection circuit). Moreover, the bias devices for the output stage can track the output transistors closely in real time over a wide range of temperatures. The result is consistent performance whether the amplifier is cold or hot and whether it plays softly or loudly.