Method and circuit for tunnel-effect programming of floating gate MOSFET transistors

A circuit for programming a MOSFET transistor to a precise output level, the MOSFET transistor having a control terminal, a first and second output terminal, and a floating gate insulated from the control terminal and the first and second output terminals by a dielectric layer, comprising:

• means connected to the first output terminal, for applying a charge thereto;
• means connected to the means for applying, for setting the charge applied by the means connected to the first output terminal as a value depending on a charge carried by the floating gate;
• means connected to the control terminal, for biasing the dielectric layer to cause charge from the means for applying to tunnel into the floating gate, until the floating gate reaches a desired charge level.

A method of tunnel-effect programming a MOSFET transistor having a control terminal, a pair of terminals including a source terminal and a drain terminal, and a floating gate region insulated with respect to said pair of terminals by a dielectric layer, the method comprising the steps of:

• connecting to a first terminal of said pair of terminals a bootstrapped capacitor, the charge state of which depends on the charge state of said floating gate region;
• and
• biasing said dielectric layer of said MOSFET transistor so that said bootstrapped capacitor causes the passage of tunneling current between said first terminal and said floating gate region and through said dielectric layer prior to said floating gate region reaching a desired charge level, thereby changing its charge state to automatically cut off passage of said tunneling current when said desired charge level is reached.

A circuit for programming a MOSFET transistor to a precise output level, the MOSFET transistor having a control terminal, a first and second output terminal, and a floating gate insulated from the control terminal and the first and second output terminals by a dielectric layer, comprising:

• means connected to the first output terminal, for applying a charge thereto;
• means connected to the means for applying, for defining the charge applied by the means connected to the first output terminal as a value depending on a charge carried by the floating gate;
• means connected to the control terminal, for biasing the dielectric layer to cause charge from the means for applying to tunnel into the floating gate, until the floating gate reaches a desired charge level.