US 8,922,249 B1Granted

Programmable CMOS-based nonlinear function synthesizer

AssigneeKing Fahd University of Petroleum and Minerals

InventorsMuhammad Taher Abuelma'atti, Saad Radhi Alabbas

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Abstract

The programmable CMOS-based nonlinear function synthesizer is a circuit that assumes that the required nonlinear function can be approximated by the summation of hyperbolic tangent (tan h) functions with different arguments. Each term of the tan h function expansion is realized using a current-controlled current-conveyor (CCCCII), or an operational transconductance amplifier (OTA)) with a different bias current. The output weighted currents of these CCCCIIs or OTAs are algebraically added to produce the output current. The present circuit can be easily integrated, extended to include higher order terms of the tan h-function expansion and programmed to generate arbitrary hard nonlinear functions. By controlling the bias current and without changing the aspect ratios of the transistors, various tan h functions with different arguments from the same topology can be obtained.

Claims10

Dependent claims

A programmable CMOS-based nonlinear function synthesizer, comprising:

a CMOS circuit having a plurality of bias inputs, a plurality of current outputs and a corresponding plurality of signal inputs, an n-th one of the current outputs in relation to its corresponding signal input defining a saturated nonlinear transfer function characterized by the relation,
tan h(αnx),
where αn is a positive integer/non-integer constant, and x represents a normalized voltage as the signal input;
weighing circuitry comprised of current mirrors operable with each output of the plurality of current outputs to form a weighted output for each said output;
summation circuitry connected to the weighted outputs, and providing an algebraic sum of the weighted outputs, the algebraic sum being characterized by the relation,
y
⁡
(
x
)
=
∑
n
=
1
N
⁢
γ
n
⁢
tanh
⁡
(
α
n
⁢
x
)
,
where current y(x) represents the required nonlinear function, and γn is a positive/negative integer/non-integer weighting factor for each value of n, where n is an integer between 1 and N, where N represents a total number of the current outputs;
and
programmable bias currents IBn connected to the bias inputs, where αn is a positive integer/non-integer constant that can be programmed by the bias inputs.

29 more elements

A programmable CMOS-based nonlinear function synthesizer, comprising:

a plurality of second generation current controlled current conveyors (CCCCIIs) each CCCCII of the plurality having a first input terminal, a second input terminal, a bias terminal accepting a programmable bias current IBn and an output terminal, the plurality arranged in a circuit in which all of the second input terminals are connected together to a common reference potential, and all of the first input terminals are connected together accepting a signal input, each CCCCII operating in a region defining a saturated nonlinear transfer function characterized by the relation,
tan h(αnx),
where αn is a positive integer/non-integer constant, n corresponds to the nth CCCCII and x represents a normalized voltage as the signal input;
weighing circuitry comprised of current mirrors operable with each said CCCCII output to form a weighted output for each said programmable output;
for each CCCCII, a corresponding current gain amplifier connected to the output terminal thereof, outputs of the amplifiers being connected together to form summation circuitry which provides an algebraic sum of the CCCCII outputs, the algebraic sum being characterized by the relation,
y
⁡
(
x
)
=
∑
n
=
1
N
⁢
γ
n
⁢
tanh
⁡
(
α
n
⁢
x
)
,
where current y(x) represents the required nonlinear function, αn is a positive integer/non-integer constant that can be programmed via the bias terminal, and γn is a positive/negative integer/non-integer weighting factor as determined by the weighing circuitry.

27 more elements

Dependencies are inferred from the claim text.