HT66FV1x0 Integrated Audio Amplifier Application Guideline
AN0486EN V1.10
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June 8, 2021
HT66FV1x0 Integrated Audio Amplifier
Application Guideline
D/N: AN0486EN
Introduction
The Holtek HT66FV1x0 series of MCUs include a 16-bit DAC for digital volume control, a class
AB audio power amplifier, SPI and UART interfaces, etc., making them applicable for use in a wide
range of home appliances, health care products, security protection and many other consumer
electronic products that require an audio function. As these MCUs contain an internal 1.5W high
power audio amplifier together with digital volume control functions, they can cater to customers’
demand for high quality sound without requiring an external power amplifier. With the advantages
of simplified external component requirements and competitive overall costs, the devices should
find excellent use in a wide range of voice playing products.
This text will take the HT66FV1x0 series as an example to introduce the operating principles,
features and usage of the MCU integrated audio power amplifier.
Functional Description
A power amplifier is the most basic device in an audio system. Power amplifiers can amplify a
weak input signal from a sound source or a pre-amplifier and then generate a current large enough
to drive the speaker for voice playing. Some common amplifier types are Class A, Class B, Class
AB and Class D.
Class A Principles
Class A is the simplest type. In a Class A amplifier, the output transistor remains in a conducting
state over the entire range of input signal cycle, i.e., the conduction angle is 360 degrees. As Class
A amplifiers operate within the linear portion of their individual characteristic curve, they have less
transient distortion and crossover distortion problems, however with low efficiency. The quiescent
operating point of the amplifier is near the midpoint of the load line. A load characteristic curve
directly reflects the relation between the load voltage and current change. The intersection of the
load line and the transistor output characteristic curve is the quiescent operating point, which is
used to analyse the circuit quiescent point and distortion situations.
