Resources Contact Us Home
Non-volatile SRAM

Image Number 5 for United States Patent #5956269.

A method and devices are provided for producing a non-volatile SRAM, of the type composed of two back-to-back, cross-coupled, CMOS inverters, each with a PMOS and an NMOS and respective outputs Q and Q.about. connected therebetween, even when the cell is completely symmetrical, by creating a stable condition wherein Q.noteq.Q.about. through rendering the threshold voltages of the NMOS devices different. The threshold voltages of the NMOSs are made different by using hot electron injection. The hot electron effect is produced by meeting the conditions, that 1) one of the NMOSs must be in saturation condition, i.e., V.sub.DS .gtoreq.V.sub.GS, where V.sub.DS is the drain to source voltage, V.sub.GS is the gate to source voltage, and the threshold voltage, of the NMOS, and 2) V.sub.DS must be large enough, typically about 7 V, depending on the fabrication process. To achieve these conditions, for example, firstly a regular write function is performed on the SRAM so that the cell will have a predetermined condition, i.e., a high, low or low, high value. A negative voltage pulse is then applied to the inverter with the high output value to put its NMOS in a saturation state. This results in producing hot electrons that are stored in the gate oxide of the NMOS, thus making the threshold voltage of the two NMOS devices unbalanced, i.e., V.sub.th1 .notident.V.sub.th2, and achieving the function of hard memory.

  Recently Added Patents
System and method for oscillator frequency control
Silicon carbide substrate, epitaxial wafer and manufacturing method of silicon carbide substrate
Method of publicly displaying a person's relationship status
Digital display devices and digital projectors with expanded color gamut
Techniques for accessing a parallel database system via external programs using vertical and/or horizontal partitioning
Low latency interrupt collector
Method for indicating the process of leaving a parking space
  Randomly Featured Patents
Support platen with removable insert useful in semiconductor processing apparatus
Low-pass filter
Thrust deflectors for propulsion nozzles of turbomachines
Freight calculation system and method of operation
Over-temperature warning system for refrigerator appliance
Ferroelectric LCD with particular rubbing directions
Control for input and output of data for use in hairdressing
Charge transfer device and a driving method thereof and a driving method for solid-state image sensing device
High power field effect transistor
Method for butt welding at least two metal sheets