Overview

The LA7780M is a downconverter for QPSK data demodulation for digital CATV transmission. This IC integrates a preamplifier, an AGC amplifier, a mixer, an oscillator, a post-amplifier, and other circuits in a single chip, and provides all the functions required from cable signal input through output to the A/D converter.

Features

• Since a preamplifier is built in, the LA7780M has adequate sensitivity to handle the input signal from the cable directly. (Input signal level:–30 to +30 dBm)

• Both internal and external AGC are supported as the AGC amplifier drive technique.

• The output amplitude of the post amplifier used to drive the A/D converter is 2 Vp-p (typical).

• Applications can be designed to use either a crystal or an inductor oscillator.

Functions

• Preamplifier

• AGC amplifier

• Mixer

• Oscillator

• Post amplifier

• IF AGC (internal/external)

• AGC detector