U4468B

Features 5-V Supply Voltage Gain-controlled 3-stage Wide-band IF Amplifier Active Carrier Generation by FPLL Principle (Frequency-Phase-Locked-Loop) for True Quadrature Demodulation Complete Alignment-free AM Demodulator Switchable Amplitude Detector for Gain Control, which Operates as a Peak Detector for FM Sound and as a Mean Level Detector for AM Sound Description The U4468B is an integrated bipolar circuit for full multistandard sound IF signal processing in TV/VTR and multimedia applications. It supplies AM signals as well as FM/NICAM sound IF signals and thus allows the design of a universal sound IF module for various applications. Quasi-split Sound Circuit and AM Demodulator IC U4468B Figure 1. Block Diagram VS 4 14 REF IF-amp Loop filter 5 FPLL 05 905 VCO 8 9 VCO IFFM 2 1 IFAM 12 Intercarrier (FM) Mean 3 AGC Peak level 13 IF AGC Mean/peak 7 S1 Mute AM-det 10 S2 6 AF (AM) Rev. 4777A–TVVCR–01/04 Circuit Description IF Amplifier and AGC The symmetrical IF input signal from the external SAW filter is fed to the pins 1 and 2. In case of FM/NICAM applications, a SAW filter with double band-pass characteristic is required for the vision and sound carrier. In case of the L-standard, a band-pass filter with the center frequency at the L-sound carrier is used. The amplifier consists of three AC-coupled wide-band IF stages. Each differential amplifier stage is gain controlled by the AGC (Automatic Gain Control) voltage, available at pin 3. The output signal...