Browse Prior Art Database

TTL Emitter Coupled Logic Converter

IP.com Disclosure Number: IPCOM000085775D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Gersbach, JE: AUTHOR

Abstract

Described is a transistor-transistor logic (TTL) to emitter-coupled logic (ECL) converter using current mirror techniques. The converter also generates its own reference voltage.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

TTL Emitter Coupled Logic Converter

Described is a transistor-transistor logic (TTL) to emitter-coupled logic (ECL) converter using current mirror techniques. The converter also generates its own reference voltage.

The TTL pulse 10 to be converted by the circuit is fed into the base of transistor T4 whose collector is coupled to voltage +V.

When this input voltage pulse 10 is low, transistors T1, T2, and T3 all act as a buffered current mirror with the current ratio of transistor T2 to transistor T3 determined by the ratio of their respective emitter resistors R2 and R3. The output voltage across resistor R1 is determined by resistor R4 and the current ratio through transistors T2 and T3.

When the input voltage pulse 10 is up, only the base current of transistor T3 flows in transistor T1 and resistor R1. Thus the voltage across R1 is nearly zero. Since the voltage across resistor R4 is proportional to that across resistor R1, the collector node 12 of transistor T2 may be used as a reference node for the output voltage.

These two outputs 11 and 12 drive an ECL circuit differentially with a difference voltage of about 200 mv. The current in transistor T3 remains constant and is switched between transistors T4 and T1 through diode D1.

The impedance at the bases of transistors T2 and T3 is low due to transistors T1 and T2 forming a negative feedback loop. The speed is, therefore, very fast.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]