SAN2202
PDS038-SA 2531/2-001 Rev. B 21-03-00
This application note describes a low-c os t add-on c ir cuit for driving an 8
Ω
-Loudspeak er to get a s imple loudhearing
(“Speakerphone”) Telephone.
To possible ways of supplying the amplifier are shown:
SAN2202a: Amplifier supply in shunt transistor path
SAN2202b: 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.
•
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
Ω
- 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
sames
samessames
sames
SAN2202
APPLICATION NOTE
SINGLE CHIP “SPEAKERPHONE” WITH
8 - OHM LOUDSPEAKER AMPLIFIER
1 Scope
2 Key Features