Amplifier Classes

Amplifier ClassDescriptionConduction Angle
Class-AFull cycle 360o of Conduction
very low efficiency at around 30%
θ = 2π
Class-BHalf cycle 180o of Conductionθ = π
Class-ABSlightly more than 180o of conduction
with conversion efficiencies reaching about 50% to 60%.
π < θ < 2π
class A
class A
class B
class B
class AB
class AB

Audio amplifier and I2S DAC

The sound wave is converted into data through a series of snapshot measurements, or samples. A sample is taken at a particular time in the audio wave, recording amplitude. This information is then converted into digestible, binary data.

The system makes thousands of measurements per second. If we can take tons of measurements extremely quickly with enough possible amplitude values, we can effectively use these snapshots to reconstruct the resolution and complexity of an analog wave.

What is an audio sample rate

The system takes these measurements at a speed called the audio sample rate, measured in kilohertz. The audio sample rate determines the range of frequencies captured in digital audio. In most DAWs, you’ll find an adjustable sample rate in your audio preferences. This controls the sample rate for audio in your project.

What is audio bit depth?

The audio bit depth determines the number of possible amplitude values we can record for each sample. The most common audio bit depths are 16-bit, 24-bit, and 32-bit. Each is a binary term, representing a number of possible values.

LM386 Audio Amplifier


The stated purpose of I2S is to facilitate the development of audio electronics by means of a standardized interface for transmission of digital data among ADCs, DACs, digital filters, digital signal processors, and other types of ICs used in audio systems. It is inherently a two-channel protocol, because it was designed for stereophonic sound
Data is driven on the SD line, the state of the WS line corresponds to the audio channel (right or left) that is currently being transmitted, and the clock line carries the serial clock.

Serial Data (SD)

  • Digital values are transmitted MSb first.
  • Transmitter and receiver do not need to have an agreed-upon word length; the transmitter sends what it has, and the receiver takes what it can use.
  • New data bits can be clocked out on the rising or falling edge of the clock. However, they must be clocked in on the rising edge, so the more straightforward approach here is the arrangement shown in the diagram below—i.e., we clock data out on the falling edge and we clock it in on the rising edge.
  • The protocol does not include unused clock periods between words; the LSb of one word is followed immediately by the MSb of the next word.

Word Select (WS)

  • A logic low on WS indicates that the word currently being transferred is part of the data stream for the left audio channel; logic high on WS indicates right-channel audio.
  • To facilitate data handling on both the transmitter and the receiver side, the WS signal transitions one clock period before the completion of a data word:


  • The protocol does not specify a maximum data rate.
  • The clock runs continuously.