Two-stage audio gain circuit based on analog-to-digital conversion and audio terminal

A two-stage audio gain circuit based on analog-to-digital conversion, comprising:

• a programmable gain amplifier (PGA) configured to receive an analog audio signal and perform programmable gain amplification processing on the received analog audio signal;
• an analog-to-digital converter configured to convert the analog audio signal after the programmable gain amplification processing into a digital audio signal and output the digital audio signal;
• a first automatic gain control (AGC) gain unit configured to perform a first AGC processing on the digital audio signal and output a first gain adjustment value to the PGA, for the PGA to perform gain adjustment on the received analog audio signal according to the first gain adjustment value;
• and
• a second AGC gain unit configured to perform a second AGC processing on the digital audio signal and output a second gain adjustment value to the PGA, for the PGA to perform gain adjustment on the received analog audio signal according to the second gain adjustment value,
• wherein both the first AGC gain unit and the second AGC gain unit comprise:
• an envelope taking unit, configured to perform absolute value processing on an audio value of the digital audio signal to take an absolution value of the audio value, and obtain an envelope curve of the digital audio signal;
• a moving average unit, configured to perform moving average processing on the envelope curve;
• an amplitude statistics unit, configured to perform statistics on an effective value of the envelope curve after the moving average processing, and output an effective statistical value;
• and
• a gain value output unit, configured to obtain and output a gain adjustment value to be adjusted according to the effective statistical value.