Line drivers extend the transmission distance between terminals or computers connected along private lines or networks. They improve connectivity across local area networks (LAN), two-wire and four-wire copper telephone lines, and leased T1 or T3 connections. Some line drivers are called short haul modems because they facilitate xDSL, VDSL, and G.SHDLS transmissions. The term xDSL refers to a family of technologies such as symmetric digital subscriber line (SDSL) and asymmetric digital subscriber line (ADSL). SDSL uses the same data rates for upstream and downstream traffic. ADSL uses different rates for each type of traffic. Very-high bit-rate digital subscriber lines (VDLS) can transmit data as far as 50 m at speeds up to 26 Mbps. G.SHDSL or G.991.2 line drivers use a form of symmetric DSL developed by the International Telecommunications Union (ITU), an organization formerly known as the CCIT. 

How to Select a Line Driver

Selecting line drivers requires an analysis of performance specifications, mounting styles, form factors, and special features. Performance specifications include supply voltage, data rate, propagation delay, pulse skew, transmission time, channel-to-channel skew, harmonic distortion and jitter. Some line drivers mount in telecommunications racks. Others are designed to stand alone or have an integrated circuit (IC) form factor. Typically, line driver features are a function of the larger communications infrastructure. For example, fiber optic networks provide data security, total electrical isolation, lightning and surge protection, and immunity from electromagnetic interference (EMI) and radio frequency interference (RFI). 

Different Form Factors and Technology Families

Line drivers with an integrated circuit (IC) form factor differ in terms of logic family and package type. Logic families for line drivers include complementary metal-oxide semiconductor (CMOS,) emitter coupled logic (ECL), and low voltage differential signaling (LVDS). CMOS uses a combination of p-type and n-type metal-oxide-semiconductor field effect transistors (MOSFET). ECL also uses transistors, but to steer current through gates that compute logical functions. Low voltage differential signaling (LVDS) line drivers provide low skew, differential signaling, and speeds up to 1350 MHz. Package types for line drivers include small outline integrated circuit (SOIC) and quad flat package (QFP). 

Standards 

DESC-DWG-78023 - MICROCIRCUITS, LINEAR, QUAD HIGH SPEED DIFFERENTIAL LINE DRIVER MONOLITHIC SILICON

GSFC-S-311-P-82 - PROCUREMENT SPECIFICATION FOR BIPOLAR MICROCIRCUITS, TYPE DS7820A DUAL DIFFERENTIAL LINE RECEIVER; TYPE DS7830 DUAL DIFFERENTIAL LINE DRIVER

MIL-M-38510/104 - MICROCIRCUITS, LINEAR, LINE DRIVERS AND RECEIVERS, MONOLITHIC SILICON

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