User Guide

NHB–3
Technical Documentation
PAMS
HF Desktop Charger CHH–8P
Original 26/97 Page 17
Microphone Amplifier and Corresponding Switches
Transistor amplifier circuit V420 and corresponding resistors and capasitors
supplies bias current for microphone. Operational amplifier N430–B is used to
amplify the microphone signal to the handphone. The gain of this amplifier is
about 40 dB. The HF microphone signal is fed to the phone through the analog
switches D400–B and D400–C. The microphone signal XMIC from the Data Ac-
cessory (X510) is fed to the phone through the switches D400–A and D400–C.
The supply voltage for the amplifier and the analog switched are taken from the
+VAN regulator N102. The +VREF reference voltage (≅ +2.75 V) is made with
the N430–A from the +VAN analog voltage (≅ +5.0 V) .
Speaker Amplifier and Corresponding Swithes
XEAR signal from the phone is fed to the HF speaker through the analog
swithes D410–C and D410–B. The signal is amplified about 17 dB with the
resistors R460, R461 and the amplifier N460. The speaker can be muted with
the MUTE–signal controlled by the prosessor.
XEAR signal from the phone can be fed to the Data Accessory (X510) through
the analog switches D410–C and D410–A.
The supply voltage +VAS (≅ +9.7 V) for the speaker amplifier is taken through
the transistor V341, controlled by the processor, from the +VA regulator N100
(≅+10.0 V).