Browse Prior Art Database

Hybrid Circuit With Large Voltage Drive

IP.com Disclosure Number: IPCOM000100142D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Gee, TW: AUTHOR [+2]

Abstract

Described is a telephone (Telco) line hybrid circuit that uses a differential drive circuit and minimum number of components. The differential configuration provides a larger peak-to-peak drive voltage than conventional configuration that provides single-ended drive voltage.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 99% of the total text.

Hybrid Circuit With Large Voltage Drive

       Described is a telephone (Telco) line hybrid circuit that
uses a differential drive circuit and minimum number of components.
The differential configuration provides a larger peak-to-peak drive
voltage than conventional configuration that provides single-ended
drive voltage.

      A typical phone line hybrid circuit suitable for use in modems
is shown in Fig. 1.

      This circuit causes signals coming in on the phone line to be
directed to the receiver.  In addition, the circuit causes the
transmitted signal coming from the transmit source to drive the phone
line.  Due to the connections of amplifier #2, no transmit signal
appears at the receiver.

      A disadvantage of this circuit is that amplifier #1 must have a
voltage swing that is twice the amount of voltage swing desired on
the phone line.  Some amplifiers, particularly amplifiers powered
from a single 5-volt supply, may not be able to deliver adequate
voltage swing.

      A solution to this problem is to use amplifier #2 along with
amplifier #1 to form a differential driver which provides twice the
voltage swing of a single amplifier (Fig. 2).  With this
configuration, the transmit signal does not appear at the receiver,
thus providing the hybrid function. Twice the voltage drive is
provided along with the hybrid function without any additional parts.
 (Note that the success of either circuit depends on the line and
Z-match being equal.) ...