CMOS Amplifier for optoelectronic receivers

Details CMOS Amplifier for optoelectronic receivers CMOS Amplifier for optoelectronic receivers

2002-05-09

2004-08-03

Nguyen, Khanh V. (Department: 2817)

Amplifiers

With semiconductor amplifying device

Including atomic particle or radiant energy impinging on a...

C330S258000

Reexamination Certificate

active

06771131

ABSTRACT:

FIELD
The present invention relates to analog circuits, and more particularly, to a CMOS amplifier with utility for optoelectronic receivers.
BACKGROUND
With increasing data rates in electronic systems, it is expected that optical interconnects (optical fibers) may in the near future replace wire interconnects at the board-to-board and chip-to-chip level. For example, a computer system such as that illustrated in
FIG. 1
may comprise one or more boards
102
and memory hierarchy
104
that exchange data packets over optical interconnects
106
. These packets may be routed via switch
108
, or perhaps the various integrated circuits may be directly connected to one another. Each board
102
may comprise one or more microprocessors.
In many applications, a photodetector provides an electrical signal indicative of a received optical signal. A typical small-signal model for a photodetector is provided in
FIG. 2
, comprising small-signal current source
202
and parasitic capacitor
204
. The small-signal current provided by current source
202
is representative of the received optical signal. The output signal is provided at output port
206
, which for many applications is connected to the input port of a transimpedance amplifier (not shown). Transimpedance amplifiers provide a small-signal output voltage signal in response to a small-signal input current signal.
In telecommunication applications, the received optical signals are typically very small due to attenuation in optical fibers, which may be hundreds of kilometers long. Consequently, a primary goal for transimpedance amplifiers for long haul communications is to provide high transimpedance with low noise amplification, while attaining as large a bandwidth as practical.
However, at the board-to-board and chip-to-chip level, such as the computer system of
FIG. 1
, attenuation is relatively negligible, and the received signals are typically orders of magnitude larger than for the case of long haul optical communication systems. In such short haul optical applications, it is desirable for economic and high-bandwidth reasons for transimpedance amplifiers to be integrated with other circuits on an integrated circuit die, such as input-output chips on boards
102
or switch
108
, and perhaps on a microprocessor itself. Accordingly, for such applications, it is desirable to provide CMOS (Complementary Metal Oxide Semiconductor) transimpedance amplifiers having an acceptable transimpedance over a relatively large bandwidth, such as, for example, 20 Gbps, with relatively low power dissipation, and with good power supply noise rejection.


REFERENCES:
patent: 5789981 (1998-08-01), Singer et al.
patent: 6344651 (2002-02-01), Woolaway et al.
Patent Application “High Bandwidth, Low Power, Single Stage Cascode Transimpedance Amplifier For Short Haul Optical Links”, Filed Mar. 26, 2002, Inventors Timothy M. Wilson, Tanay Karnick, 16 pages; 7 pages of figures.

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