Abstract: The invention concerns a stylus for producing a high-voltage, sinusoidal signal for an electrostatic digitizing pad. The high voltage is obtained by applying a sine wave to one lead of the primary of a transformer, and applying the inverse of the sine wave to the other lead of the primary. The secondary of the transformer produces the high voltage, which is developed into a signal which is applied to the digitizing pad.

Abstract: An oscillator circuit having a first node oscillating with a first indeterminate duty cycle and having a second node oscillating with a predetermined second duty cycle. Both nodes oscillate at similar frequencies. A variable current source and a switch are coupled in series between Vcc and ground with the output of the variable current source being the second node. The first node controls the switch, which is closed when the first node is at a first logic state and is opened when it is at a second logic state. During each cycle, a monitoring circuit measures the time span that the first node is at the first logic state and adjusts the magnitude of the variable current source to make it directly proportional to the measured time span. By adjusting the variable current source, the second node can be made to reach a desired voltage level in a desired amount of time during each cycle. In a second embodiment, a current limiting transistor is inserted between the second node and the switch.

Abstract: The invention concerns digitizing tablets in portable computers, wherein position of a stylus, located on the tablet, is computed. The invention corrects for various errors which creep into the computation, in order to produce a more accurate stylus position. The digitizing tablet has multiple sensors used to determine the stylus' position with respect to the digitizing tablet. Error signals are generated by measuring the sensors outputs when the stylus is not inducing a signal into the digitizing tablet. In one embodiment, these error signals are used to modify certain parameters used in calculating the stylus position.

Abstract: The invention concerns a stylus for producing a high-voltage, sinusoidal signal for an electrostatic digitizing pad. The high voltage is obtained by applying a sine wave to one lead of the primary of a transformer, and applying the inverse of the sine wave to the other lead of the primary. The secondary of the transformer produces the high voltage, which is developed into a signal which is applied to the digitizing pad.

Abstract: The present invention discloses an integrated constant bias voltage generator using only active devise to simulate a high impedance node, as seen from a capacitively coupled input signal. A reference current source an MOS device are coupled in series between Vcc and ground with the drain electrode of the MOS device being the constant bias voltage output. An input signal capacitively coupled to said drain electrode introduces an error current monitored by a current monitoring means. A feedback means responsive to the current monitoring means modulates the control input of the MOS device to select a IDS vs. VDS characteristic curve which will maintain the VDS voltage constant for any given IDS current, including the error current. The feedback means also compensates for voltage fluctuations in Vcc.

Abstract: The invention concerns a stylus for producing a high-voltage, sinusoidal signal for an electrostatic digitizing pad. The high voltage is obtained by applying a sine wave to one lead of the primary of a transformer, and applying the inverse of the sine wave to the other lead of the primary. The secondary of the transformer produces the high voltage, which is developed into a signal which is applied to the digitizing pad.

Abstract: A nonvolatile memory device comprising first and second transistors connected between respective first and second terminals and a reference potential terminal, the transistors having first and second floating gates, respectively, for storing complementary charges. The device further comprises first and second input lines capacitively coupled to the gates, and means for providing a biasing voltage slightly in excess of the threshold voltage of the transistors to the input lines.

Abstract: A multiplying digital to analog converter using ladder networks and binary weighted load compensation to allow integration and video frequency operation. In one form, the circuit is configured from field effect transistors which incorporate by virtue of their structural and operational characteristics both the switching and resistive functions of R-2R ladder networks. The circuit is used to convert digital format words representing intensity and color (red, green and blue) into analog red, green and blue display drive signals. According to that configuration, the output of the digital to analog intensity word converter serves as the reference for the three digital to analog color word converters. Loading effects attributable to differences in the bit content of the color words are offset by a binary weighted switched load which is responsive to a digital compensation word. The switched load is also connected to the output of the intensity word converter.

Abstract: A multiplying digital to analog converter using ladder networks and binary weighted load compensation to allow integration and video frequency operation. In one form, the circuit is configured from field effect transistors which incorporate by virtue of their structural and operational characteristics both the switching and resistive functions of R-2R ladder networks. The circuit is used to convert digital format words representing intensity and color (red, green and blue) into analog red, green and blue display drive signals. According to that configuration, the output of the digital to analog intensity word converter serves as the reference for the three digital to analog color word converters. Loading effects attributable to differences in the bit content of the color words are offset by a binary weighted switched load which is responsive to a digital compensation word. The switched load is also connected to the output of the intensity word converter.