MC34018M/TR

The MC34018 integrates the necessary amplifiers, attenuators, and several control functions for a high-quality hands-free speakerphone system. It includes a microphone amplifier, a speaker audio power amplifier, transmit and receive attenuators, a background noise level detection system, and an attenuator control system that responds to transmit and receive levels relative to background noise. The circuit also incorporates all regulated power supplies required for internal and external circuitry, allowing operation from the telephone line voltage without the need for an additional external power supply. With a single external potentiometer for volume control, the MC34018 is suitable for use as a speakerphone in residential and commercial systems, intercom systems, car phones, and other applications.

Applications

• Home and commercial systems
• Intercom systems
• Automotive telephone

Key features

• Integrates all essential level detectors and attenuator control circuitry for speakerphone handset applications on a single monolithic IC
• Long-term stable background noise level monitoring
• Wide dynamic operating range through signal compression
• On-chip power supply and reference voltage regulation circuitry
• Typical output power of 100mW into a 25-Ω load with minimal distortion
• Active/standby operating mode selectable via a single pin
• Linear volume control function
• Available in standard 28-pin plastic DIP or SOP package