Binary-Weighted Tunable Resistor DAC

Technology #3843

A digital to analog converter (DAC) includes an operational amplifier and a plurality of ladder elements. Each ladder element includes an epot for providing a voltage, a capacitor, and a switch for selecting between a first voltage and a reference voltage, and for providing the first selected voltage to the first capacitor. The output of the ladder elements are coupled to the inverting input of the operational amplifier. Alternatively, the ladder elements may use tunable floating-gate resistors.

The present invention provides a digital to analog converter (DAC) using floating-gate technology. Various embodiments of the present invention overcome the deficiencies in the prior art, by providing a small, low power, and accurate DAC suitable for fabrication in standard CMOS technologies.

The digital to analog converter includes an operational amplifier, and a plurality of ladder elements. Each ladder element includes an epot for providing a voltage, a capacitor, and a switch for selecting a first voltage or a reference voltage as a selected voltage. The epots may provide the selected voltage to the input of the capacitor. The output of the ladder elements are coupled to the inverting input of the operational amplifier.

The digital to analog converter includes an operational amplifier, and a plurality of ladder elements. Each ladder element includes a floating gate tunable resistor, and a switch for alternatively connecting the input of the floating gate tunable resistor to either a first voltage or to a second voltage. The output of the ladder elements are connected to the inverting input of the operational amplifier.

The floating gate tunable resistor may include a programming circuit having a first floating gate transistor with a first source, a first floating gate, and a first drain. The floating gate tunable resistor can further include a resistor circuit having a second floating gate transistor with a second source, a second floating gate, and a second drain. The first floating gate of the programming circuit and the second floating gate of the resistor circuit are electrically coupled together.