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High-Speed Video Amplifier Using Emitter-Coupled Logic Circuits As a Current Source

IP.com Disclosure Number: IPCOM000046236D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Aoki, T: AUTHOR

Abstract

This video amplifier utilizes two integrated circuits (ICs) each having one or more emitter-coupled logic (ECL) circuits, wherein paired ECL circuits are coupled together to form a differential current source for the separate output transistor. The ECL circuits so coupled are connected between differential input terminals and the output transistor without requiring a conventionally used biasing circuit or differential amplifier.

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High-Speed Video Amplifier Using Emitter-Coupled Logic Circuits As a Current Source

This video amplifier utilizes two integrated circuits (ICs) each having one or more emitter-coupled logic (ECL) circuits, wherein paired ECL circuits are coupled together to form a differential current source for the separate output transistor. The ECL circuits so coupled are connected between differential input terminals and the output transistor without requiring a conventionally used biasing circuit or differential amplifier.

The basic circuitry of Fig. 1 utilizes two ECL circuits contained in IC1 and IC2, respectively. The output terminals of the ECL circuits are connected together, and resistor R2 is connected between the output terminals and a voltage source VE, thereby forming a differential amplifier. Terminal VCl from one of the ECL circuits is connected to the emitter of the output transistor T1, while terminal VCl of the other ECL circuit is grounded. The base of transistor Tl is connected to a constant voltage source VB so that it operates as a common base transistor. The collector of transistor Tl is connected to the final output terminal and to a voltage source VD via resistor R1. A pair of differential input voltages +V1 and - V1 are applied to the ECL circuits in opposite polarities.

In the basic circuitry of Fig. 1, two ECL circuits operate as a current source for transistor T1 and voltage VO at the final output terminal is represented as follows:

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