In this tutorial, I am going to show a I/O expander method using PCF8574A, which is a 8 bit I/O expander using I2C bus. This is another alternative other than using shift registers to expand either inputs or outputs such as 74HC595 (outputs) or 74HC165 (inputs). One of the advantages of using PCF8574A I/O expander is that it uses I2C bus, which requires only two data lines, they are clock (SCK) and data (SDA). Therefore, with these two lines, you can control up to eight of the same chip by changing the address input, providing extra 64 I/O pins.
Today, I am going to share on how you can make a low voltage audio amplifier. For this project, I am using LM 386 Audio Amplifier, which is commonly used among electronics hobbyist. I will break the article into a few sections. First, I will explain about the LM 386 chip itself. Then move on with some explanation on the parts used in this project. And finally, the design of audio amplifier.