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Multiple Output Current Source with High-Precision Path

IP.com Disclosure Number: IPCOM000118273D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Tanghe, SJ: AUTHOR

Abstract

Disclosed is a current mirror with multiplexors which provides multiple output currents simultaneously or single output currents with enhanced accuracy. Enhanced accuracy is achieved by bypassing the current mirrors using a novel multiplexing scheme.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Multiple Output Current Source with High-Precision Path

      Disclosed is a current mirror with multiplexors which provides
multiple output currents simultaneously or single output currents
with enhanced accuracy.  Enhanced accuracy is achieved by bypassing
the current mirrors using a novel multiplexing scheme.

      In certain applications, there is a need to drive current into
several loads at once.  This can be done by mirroring a reference
current to provide multiple outputs.  However, this method reduces
the accuracy of the output currents since the mirrors are not ideal.
At times when a single output is required, higher accuracy is
desired.

      Ultimately, a current must get from the output of a reference
generator (on the left in the attached Figure) to a single selected
load (see bottom of Figure) in Single Output (SO) mode, where only
one load is to be activated.  In Multiple Output (MO) mode, copies of
the current must be made available to all loads simultaneously.
However, when the reference current is copied using standard current
mirrors, the precision of the current is reduced.  This may be
acceptable in MO  mode but for normal SO mode, this degradation is
unacceptable.

      For every channel, there is an associated two-input multiplexor
('MUX' in Figure) that controls the path of current flow to the
loads.  The output of the multiplexor leads to the load.  Current can
flow into the multiplexor from two paths.  One input path is common
for all multiplexors and comes from the precision reference current
source.  The other inputs come from a current mirror that makes
separate copies of the reference current.  The inputs from the
current mirror are  not common to each other.

OPERATION:  MULTIPLE OUTPUT MODE

      In MO mode, the bank control signal (labeled 'B' in the Figure)
is active, turning on the associated switches (shown as FETs for
simplicity).  The input current must come from the refere...