Video Distribution Amplifier

EE JULY/AUGUST 1988 The Type TEA5114 from Thomson-CSF comprises three electronic switches fol- lowed by a buffer/amplifier. Normally the voltage amplification is 2 (6 dB). When the input voltage exceeds 1.2 Vpp, or when the output voltage ex- ceeds 1.5 Vpp, an internal selector reduces the amplification to unity (0 dB). The threshold of 1.2 Vpp is created with the aid of voltage divider R4-R5, which also forms the input termination of 75 Q. Series resistors R,-R3 ensure 75 Q output impedance for driving video equip- ment via standard coax cable. The TEA5114 can be used as a video source selector also, provided each input has its own 75 Q termination network. The non-connected inputs should then be fitted with a coupling capacitor. Chan- nel selection is effected by controlling the logic level at pins 10, 12 and 15. Note that the logic 1 (high) level corresponds to +2.5 V here. 1 Parts list Resistors (±5%): ...R3 incl. =15R R4 = 47R R5 = 27R Capacitors: CI ...C4 incl.=100n Semicon...