TSH512 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TSH512' PDF : 32 Pages View PDF
General description
TSH512
5.6
PEA section: pre-emphasis
The amplitude-regulated audio coming from the ALC feeds the positive input of the
operational amplifier called PEA (pre-emphasis). The pre-emphasis consists in a high-pass
filter in order to compensate the behavior of the FM transmission.
Figure 32. Pre-emphasis schematics
RPEA1 and CPEA1 set the time constant of the pre-emphasis as:
τ = RPEA1. CPEA1
50 µs or 75 µs time constants are generally used.
Choosing the gain of the PEA stage also allows one to set the right modulation level to the
varicap diode. The gain in the passband is:
GPEA = 1+ (RPEA2/RPEA1)
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Doc ID 8120 Rev 7
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