Panasonic AN 22023 free download

File name SAN2202.pdf

sames SAN2202 APPLICATION NOTE SINGLE CHIP "SPEAKERPHONE" WITH 8 - OHM LOUDSPEAKER AMPLIFIER 1 Scope This application note describes a low-cost add-on circuit for driving an 8-Loudspeaker to get a simple loudhearing ("Speakerphone") Telephone. To possible ways of supplying the amplifier are shown: SAN2202a: SAN2202b: Amplifier supply in shunt transistor path Amplifier supply by power extraction circuit (SAN3020) It can be added to any SA253x application without interfering with PTT-relevant parameters, like AC-impedance, Sidetone cancellation or DC-mask. 2 Key Features · Low cost additional circuit enables use of loudhearing function · Full duplex "handsfree" operation via handset microphone and loudspeaker (at distances <2m between · · · · · · · telephone and user) Can be added to any SA253x- application Enables use of low cost 8 - Loudspeaker High output power with low distortion Entirely powered from the telephone line No influence of loudspeaker amplifier in AC-impedance, sidetone cancellation or DC-mask Loudspeaker volume adjustable by potentiometer Excellent sidetone cancellation of SAS253x circuits enables high loudspeaker volume without howling between handset microphone and loudspeaker SAN2202 PDS038-SA2531/2-001 Rev. B 21-03-00 SAN2202 TABLE OF CONTENTS 1 SCOPE...1 2 KEY FEATURES ...1 3 OTHER APPLICABLE DOCUMENTS AND PAPERS ...3 4 REVISION STATUS ...3 5 GENERAL DESCRIPTION ...3 5.1 AMPLIFIER SUPPLY: COMPARISON OF SAN2202A AND SAN2202B: ...3 6 BLOCK DIAGRAM ...4 6.1 HOW TO AVOID HOWLING ...4 7 CIRCUIT DESCRIPTION ...