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CIRCUIT TOPOLOGY TO REDUCE CROSS TALK BETWEEN SELECTED AND UN-SELECTED PRE AMP INPUTS

IP.com Disclosure Number: IPCOM000014858D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 4 page(s) / 69K

Publishing Venue

IBM

Abstract

The typical cross talk number from selected to unselected preamp inputs for existing preamp modules is between 55 to 70 dB. The topology described below and illustrated above will give cross talk isolation of at least 85 dB. This isolation is very important in the tape products because of the noise conditions that exist on the deselected head inputs. The high noise conditions

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  CIRCUIT TOPOLOGY TO REDUCE CROSS TALK BETWEEN SELECTED AND UN-SELECTED PRE AMP INPUTS

The typical cross talk number from selected to unselected preamp inputs for
existing preamp modules is between 55 to 70 dB. The topology described below
and illustrated above will give cross talk isolation of at least 85 dB. This
isolation is very important in the tape products because of the noise
conditions that exist on the deselected head inputs. The high noise conditions

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on the deselected readers is due to the fact that active write head lines are
next to the deselected read lines in the head cable. In current high end tape
products, either separate desecrate FET switch devices are used to short out
the deselected preamp inputs or separate preamp modules are used. Either of
these solutions involves added cost and complexity at the card. The new
topology described eliminates the added complexity and cost by not requiring
external FET devices or separate preamp modules.

The above topology has a number of unique features that will not be found in
any other tape or disk drive preamp module. The first is the addition of the
block called "Short Node" to each of the preamp inputs. The purpose of this
block is to short the node to ground when it is not being used. This is done
with an FET transistor. By shorting the node, the signal going to the
deselected preamp input is reduced. The second is the fact that each preamp
differen...