Ecl and ttl to cmos logic converter

Abstract

A logic converter enables a digital logic product to work with either an ECL signal input or a TTL signal input without any need of modifying or reconfiguring the product. In particular, the logic converter converts digital input signals of a first logic type (for example, ECL) to digital output signals of a third logic type (for example, CMOS). It also converts digital input signals of a second logic type (for example, TTL) to digital output signals of the third logic type. A first operational transconductance amplifier circuit including a first differential amplifier using a differential transistor pair of a first conduction type receives digital input signals of the first logic type and converts the digital input signals to digital output signals of the third logic type. A second operational transconductance amplifier circuit including a second differential amplifier using a differential transistor pair of a second conduction type receives digital input signals of the second logic type and converts the digital input signals to digital output signals of the third logic type. Circuitry causes only one of the first differential amplifier and the second differential amplifier to be active at a time depending on which logic type of digital input signal is being received. The circuitry for causing only one differential amplifier to be active includes a first level shifting circuit connected to the first differential amplifier and a second level shifter circuit connected to the second differential amplifier.