TRAC020LH Zetex Inc., TRAC020LH Datasheet - Page 6

• Manufacturer Part Number: TRAC020LH
• Description: Totally Re-configurable Analog Circuit - Trac
• Manufacturer: Zetex Inc.

CELL FUNCTION DETAILS
ADD (code 011)
Can be represented as an operational
amplifier with three resistors of equal value R.
The virtual earth at the inverting input gives:-
E
The output is the inverted sum of the input
voltages.
NEGATE (code 010)
The negate function is provided by an adder,
but with only one input, therefore E
NON INVERTING PASS (code 100)
Used for topological reasons. It provides a
route through the cell with no modification. i.e.
a unity gain amplifier
LOG (code 110)
Can be represented as an operational
amplifier with a pair of back to back diodes in
the negative feedback loop and an input
resistor R. The virtual earth at the inverting
input gives:-
E
where
k = Boltzmann’s constant
T = absolute temperature
q = electron charge
I
ANTI - LOG (code 101)
Similar to the log circuit except that the diodes
and resistors are reversed. The output voltage
is therfore given as :-
E
When the signal is processed through both log
and anti-log the magnitude of the saturation
current and absolute temperature cancel.
o
o
o
o
=saturation current
TRAC020LH
= -kT/q log (E
= -RI
= -R(E
o
(exp qE
a
/R + E
b
a
a
/R) = - (E
/RI
/KT - 1)
o
+ 1)
a
+ E
b
)
o
=-E
b
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