Texas Instruments Corporation

Michael H Haight

William H Giolma

Mark A Wolfe

Richard Edward Boucher

An LCD drive circuit includes a voltage divider circuitry which generates a plurality of voltages (V.sub.1 -V.sub.5) in response to a reference voltage. A substantially constant reference voltage is generated by a band-gap reference circuit (22). A digital-to-analog converter (32) allows the voltages to be adjusted responsive to digital control signals.

Liquid crystal display driver and driver method

A read/write configuration (44) is provided for switching signals between a source (46) and either a single output (60) or a plurality of outputs (60) and (62). A control circuit (68) operates to control a signal switching circuit (64) and a power supply switching circuit (66) in response to a control signal input thereto. More particularly, in a reading mode, the switches within signal switching circuit (64) are opened while the switch within power supply switching circuit (66) is closed. Further, in a writing mode, the switches within signal switching circuit (64) are closed while the switch within power supply switching circuit (66) is opened.

Read/write switching circuit

A self contained circuit to enable a tank type (coil/capacitor) voltage controlled oscillator to start up and free run from a known state. The circuit allows the oscillator to be stopped to within two periods by invoking its only input logic signal and also restarted with no adverse effects on its free running operation. It includes three current mirrors, one which sets the current for the other two mirrors and of the final two, one actively sets a bias on a coil (stops oscillation) while the other makes up for the lack of coil bias by providing an equivalent amount current influx to the oscillator in the free running condition.

Zero phase startup for a tank type voltage controlled oscillator

An oscillator circuit having a coil and capacitor tank circuit, a clamp resistor connected at one end to the coil and a switch coupled to the clamp resistor and coil. The switch is operative to close in response to a first input logic clamp signal and shunt the coil with an impedance that causes the oscillation to stop quickly. In response to removal of the input logic clamp signal the tank circuit starts to oscillate from a known state. Preferably the clamp resistor has a value which equalizes the tank currents for the clamped and peak unclamped states.

Voltage controlled oscillator clamp circuit

A voltage controlled oscillator circuit of a type having a tank circuit for generating oscillations which includes a means for establishing a fixed bias voltage with respect to ground at a bias end of said tank circuit, means for drawing current from an a.c. end of said tank so as to control the tank gain, and an AGC capacitor. A constant current source is coupled to the AGC capacitor for supplying it with a constant charging current. Means are provided for discharging the AGC capacitor at a voltage level determined by a ratio of resistors and a transistor emitter-base ratio.

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Pottsboro, TX, United States of America

Michael H Haight