Nonvolatile nonlinear programmable electronic potentiometer

A variable impedance circuit which provides a specified electrical impedance between first and second terminals, said variable impedance circuit comprising:

• impedance controlling means for controlling the electrical impedance between said first and second terminals, said impedance controlling means including input means for receiving electrical signals specifying the impedance between said first and second terminals and first storage means for storing a value representative of said specified impedance;
• variable impedance network means responsive to the value stored in said first storage means for setting the impedance between said first and second terminals, said variable impedance network means comprising a first variable impedance network having first, second and wiper terminals, and including a plurality of impedance elements interconnected at a plurality of nodes so as to create a fixed impedance between said first and second terminals, one terminal of at least one of said impedance elements connected to said first terminal and one terminal of another one of said impedance elements connected to said second terminal, said wiper terminal selectively coupled to one of said nodes as a function of said impedance controlling means;
• and second variable impedance network means having third and fourth terminals, said third terminal being connected to one of said first and second terminals, said fourth terminal being connected to said wiper terminal, said second network means including a plurality of series connected impedance elements and having a node between each pair of impedance elements, said third terminal being connected to the first said impedance element which is not connected to a said node, means for coupling a selected one of said nodes, or the terminal of the last impedance element in said series which is not connected to a said node, to said wiper terminal, said coupling means being controlled by said impedance controlling means;
• second storage means for storing the value stored in said first storage means in response to a first electrical storage signal, the value stored in said second storage means remaining therein in the absence of electrical power;
• and
• means for causing the value stored in said second storage means to be stored in said first storage means in response to a second electrical storage signal.

A variable impedance circuit which provides a specified electrical impedance between first and second terminals, said variable impedance circuit comprising:

• impedance controlling means for controlling the electrical impedance between said first and second terminals, said impedance controlling means including input means for receiving electrical signals specifying the impedance between said first and second terminals and first storage means for storing a value representative of said specified impedance;
• variable impedance network means responsive to the value stored in said first storage means for setting the impedance between said first and second terminals, said variable impedance network means comprising a ladder network including a 1R-2R type resistor ladder circuit of N stages, each having an input 2R resistor and an output 1R resistor, said impedance controlling means including means for selectively coupling said first terminal to a selected first one of said input resistors and for coupling said second terminal to a second selected one of said input resistors;
• a third terminal connected to one of said output resistors;
• second storage means for storing the value stored in said first storage means in response to a first electrical storage signal, the value stored in said second storage means remaining therein in the absence of electrical power;
• means for causing the value stored in said second storage means to be stored in said first storage means in response to a second electrical storage signal;
• and
• control means coupled to said input means for changing the value stored in said first storage means.