SAN2202
APPLICATION NOTE
sa me s
SINGLE CHIP “SPEAKERPHONE” WITH
8 - OHM LOUDSPEAKER AMPLIFIER
1 Scope
This application note describes a low-cost add-on circuit for driving an 8Ω-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
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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)
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Can be added to any SA253x- application
Enables use of low cost 8Ω - 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
SAMES [ SAMES ]
