Abstract:
A threshold voltage generator for a field-effect transistor, being of a type adapted to compensate for variations of the threshold voltage from a nominal value, comprising a first amplifier having a first input connected to a current generator; a second amplifier connected ahead of a second input of the first amplifier and having an input connected to another current generator; and a third amplifier connected after the first amplifier and having an output adapted to produce the value of said threshold voltage.
Abstract:
Transducers formed as part of a touchscreen system emulate the motion of a pushbutton or other mechanical elements. A touchscreen system positions a transducer adjacent to an icon displayed on the touchscreen surface. When a user touches the icon, the transducer senses the touch and is then deformed in a pattern that emulates a mechanical motion, giving the user the sensation of touching a mechanical button. An excitation signal applied to the transducer is compared to a target excitation signal that, when applied to the transducer, causes the transducer to emulate the desired motion. When any differences between the two signals are detected, the excitation signal is adjusted so that the motion is corrected. The target excitation signal, or time and voltage segments defining it, are stored in memory and retrieved for comparison. The excitation signal is also selected to reduce any acoustic artifacts that can cause the transducer to generate audible clicks.
Abstract:
A transceiver for an ultrasonic imaging device includes a transmit circuit and a receive circuit. The transmit circuit outputs test pulses to a probe including a transducer to generate an image of a test object. A composite signal including the test pulses and a reflected signal is output by the transducer. The receive circuit receives the composite signal including the test pulses and the reflected signal and includes a filter circuit. The filter circuit filters the test pulses from the composite signal and passes the reflected signal. An impedance of the filter circuit is equal to substantially zero when the reflected signal is within a predetermined frequency range.
Abstract:
A driver circuit includes a CMOS stage and switch functionalities for performing certain tasks. One task is to selectively block exposure of the CMOS stage to reference voltage(s). Another task is to selectively protect the CMOS stage during transient operation. Yet another task is to block leakage current from flowing from the CMOS stage to ground.
Abstract:
A write driver driving a write current through a head connected to the write head by an interconnect. The write driver includes a circuit matching output resistance to the odd characteristic impedance of the interconnect and a voltage boosting circuit. The voltage boosting circuit in connected between a high voltage reference or supply voltage and a low voltage reference, and includes a current source, such as a MOS transistor, connected to the input node of a capacitor. During the overshoot duration, the current source operates at saturation to generate a pulsed current with an amplitude of half the load current. The circuit includes another transistor in series with the current generator between the capacitor and the driver output. A forward bias diode is connected between the capacitor output node and high voltage reference and enters reverse bias during overshoot duration swinging the driver output voltage above supply voltage.
Abstract:
A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device and a current sink circuits coupled to each terminal of the write head, for selectively sourcing current to and sinking current from the write head, respectively. A clamp device is coupled to each write head terminal to selectively clamp the write head terminals to steady state intermediate voltage levels. The circuit further includes a control circuit for individually activating the pull-up devices, the current sink circuits and the clamp devices. In particular, when reversing the direction of current flow through the write head from a first direction in which current is provided to the write head via the write head terminal to a second direction in which current is drawn from the write head from the write head terminal, the appropriate pull-up device is activated for a predetermined period of time. The clamp device coupled to the temporarily activated pull-up device is thereafter activated to clamp the corresponding write head terminals to the steady state intermediate voltage levels.
Abstract:
A method and circuit is disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device coupled to a terminal of the write head, for selectively providing a current to the write head through the terminal. The circuit further includes parallel-connected first and second current sink circuits, each of which is coupled to the write head terminal and selectively activated to draw current from the write head via the write head terminal. The circuit further includes a control circuit for individually activating the pull-up device and the first and second current sink circuits. In particular, when reversing the direction of current flow through the write head from a first direction in which current is provided to the write head via the write head terminal to a second direction in which current is drawn from the write head from the write head terminal, both the first and second current sink circuits are activated by the control circuit. When the current in the write head nears the desired destination current level, the second current sink circuit is deactivated and the pull-up device is thereafter immediately activated for a predetermined period of time. The pull-up device is deactivated as the current in the write head approaches a constant value. Due to the deactivation of the second current sink circuit and the temporary activation of the pull-up device, current overshoot and undershoot of the write head current is minimized.
Abstract:
A device comprises a variable-gain input amplifier, a low-pass analog filter, a transversal continuous-time analog filter, and two distinct and parallel sampling channels interposed between the transversal analog filter and an RLL-NRZ decoder. The two sampling channels each comprise an analog-to-digital converter and a Viterbi detector arranged in series and operating according to sampling sequences that alternate with one another.
Abstract:
An integrated circuit transconductor stage which suppresses the dependence on temperature and production process variables of a differential transconductor stage. A negative feedback relation is used, where the output of the transconductor stage is connected to an additional current generator (which is referenced to a precision external resistor), to a capacitor, and also to the gate of a PMOS transistor which sources current to a polarization stage, which in turn sources current to the transconductor stage, or to multiple transconductor stages.
Abstract:
A transceiver for an ultrasonic imaging device includes a transmit circuit and a receive circuit. The transmit circuit outputs test pulses to a probe including a transducer to generate an image of a test object. A composite signal including the test pulses and a reflected signal is output by the transducer. The receive circuit receives the composite signal including the test pulses and the reflected signal and includes a filter circuit. The filter circuit filters the test pulses from the composite signal and passes the reflected signal. An impedance of the filter circuit is equal to substantially zero when the reflected signal is within a predetermined frequency range.