Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Resonance Inhibitor for Gbps Optical Receivers

IP.com Disclosure Number: IPCOM000103799D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 66K

Publishing Venue

IBM

Related People

Larsen, TA: AUTHOR

Abstract

Disclosed is a circuit technique which eliminates very high frequency resonances in the fiber-optic receiver circuit consisting of a photodiode and the first stage amplifier and associated interconnect wiring. Specifically, a resistor is placed at the input of the first stage amplifier as close to the input as physically possible. Typically, the resistor value would be 25 to 100 ohms.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Resonance Inhibitor for Gbps Optical Receivers

      Disclosed is a circuit technique which eliminates very high
frequency resonances in the fiber-optic receiver circuit consisting
of a photodiode and the first stage amplifier and associated
interconnect wiring.  Specifically, a resistor is placed at the input
of the first stage amplifier as close to the input as physically
possible.  Typically, the resistor value would be 25 to 100 ohms.

      Figure 1 illustrates the circuit details.  The photodiode of a
1 gb/s fiber-optic receiver is typically a discrete diode and the
interconnect wiring between the photodiode and the first-stage
amplifier, generally a transimpedance amplifier, is represented as an
L-C network at these high frequencies.  The transimpedance amplifier,
a current to voltage amplifier, appears as a relatively low input
impedance to the network.  At some very high frequencies, due to the
feedback network, the amplifier's input resistance may become very
small, in fact, may actually appear as an input impedance with a
negative real part.  The combination of very small or negative real
part of the input impedance, coupled with an external L-C network,
can result in a resonance at the frequency in which the loop
impedance has a zero imaginary component and a very small or negative
real component.  In fact, from experimental evaluations, resonances
do occur under some conditions of specific wiring and photodiode
characteristics.  In order to avoi...