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Amplifier With Adjustable Transimpedance for Controlling Bandwidth of a Data Signal for Rejecting Noise Above the Signal Frequency

IP.com Disclosure Number: IPCOM000102767D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 56K

Publishing Venue

IBM

Related People

Boerstler, DW: AUTHOR

Abstract

In a known circuit, a first stage has a bipolar transistor connected as an inverter, a second stage has a bipolar transistor connected as an emitter follower, and a resistor is connected between the emitter terminal of the second transistor and the base terminal of the first transistor to form an amplifier having a selected gain. The value of the resistor is designated Rf.

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Amplifier With Adjustable Transimpedance for Controlling Bandwidth of a Data Signal for Rejecting Noise Above the Signal Frequency

      In a known circuit, a first stage has a bipolar transistor
connected as an inverter, a second stage has a bipolar transistor
connected as an emitter follower, and a resistor is connected between
the emitter terminal of the second transistor and the base terminal
of the first transistor to form an amplifier having a selected gain.
The value of the resistor is designated Rf.

      This circuit is called a transimpedance amplifier because its
gain can be analyzed in terms of the ratio of its output voltage and
its input current.  A signal current at the base terminal of the
first stage varies in time and is designated i(t).  This signal
source may be a semiconductor light-producing device having a
polarity invariant voltage designated vs bias.  The output voltage
across the emitter resistor of the second stage is substantially the
product of the input current i(t) and the resistance Rf.

      In a circuit that is improved for use with optical fiber
communications apparatus, the resistor is replaced by a field effect
transistor (FET) that has its gate terminal connected to a source of
potential designated Vrf.  The value of this resistance, called the
source drain resistance, is designated Rf and is a function of Vrf.
Resistance Rf can be varied over a wide range by varying Vrf.

      It is a characteristic of these circ...