Samsung SPH-A900 Service Manual page 9

2-1-8. Speaker Path
When the MSM(ucp102) receives the data, its internal CMX generates bell and melody. The CMX bell
and melody generated in MSM6500 are sent to SAPA1D2.
The SAPA1D2 (stereo class - D audio power amplifier) is a high quality audio power conversion chip
generating 2.5W RMS output directly from the V_BAT supply. It is a high efficiency audio amplifier for
mobile applications. The gain of amplifier in SPH-A900 set to 4(V/V) . The output generated in SAPA1D2
is intended to drive two speakers.
2-1-9. Key Tone Generator
The CODEC data out from the MSM6500 is converted to DTMF signal by TONE generator of internal
CODEC, which is then amplified by the internal audio amplifier to be sent to the speaker units.
2-2. PCS Section
2-2-1. Receiver
LOW NOISE AMPLIFIER (U300)
The low noise amplifier(It is included in RFL6000 : U300) amplifies a weak signal received from the base
station to obtain the optimum signal level.
RF BAND PASS FILTER (F300)
The RF BPF(F300) passes only a specific frequency(1960±30 MHz) from the signal received from the
mobile station. The bandwidth is 60 MHz.
VOLTAGE CONTROLLED OSCILLATOR(VCO300)
The VCO(VCO300) generates the signal having 1715 ~ 1788MHz frequency range.
The VCO's output frequency is changed by control voltage. The PLL in S1M8690X generates this control
signal and this signal is changed into DC control voltage by R-C Loop filter.
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2-5
Circuit Description