Patent ID: 8849219
Filing Date: 2014-09-30
Classification: H03M

Abstract:
1. A DA converter configured to convert a digital signal comprising n (n>1) bits to an analog current to output the analog current from an output terminal, the DA converter comprising n voltage-current converters each of which corresponds to each bit of the digital signal and is configured to generate a current depending on the corresponding bit, wherein a k-th (k is an integer of 0 to n−1) voltage-current converter comprises a first switch, a first transistor whose threshold voltage is adjustable, and a second switch which are connected in series, wherein the first switch is controlled by a value of the k-th bit of the digital signal or a first control signal, the first control signal being a signal for adjusting the threshold voltage of the first transistor, the second switch is controlled by a second control signal for adjusting the threshold voltage of the first transistor, the first transistor comprises: a semiconductor substrate to which a reference voltage or a program voltage for adjusting the threshold voltage of the first transistor is applied; a first diffusion region and a second diffusion region separated from each other in the semiconductor substrate, the first diffusion region being connected to the first switch, the second diffusion region being connected to the second switch; an insulating film on the semiconductor substrate between the first diffusion region and the second diffusion region; a charge accumulating film on the insulating film, the charge accumulating film being capable of accumulate a charge; and a gate on the charge accumulating film, the program voltage or a predetermined bias voltage being applied to the gate.