System and method for controlling the slew rate of a signal

摘要

Techniques for controlling the slew rate of a signal independently of RC time constants are disclosed. In one embodiment, a gate driver circuit for an LCD panel may include a rail-to-rail operational amplifier having an output stage configured to produce a gate activation signal for switching pixels of the LCD panel. A slew rate control circuit may be provided for adjusting the slew rate of the gate activation signal by varying a bias current of the output stage relative to a compensation capacitance and a gain of the operational amplifier. For instance, the slew rate may be increased by increasing the bias current, and decreased by decreasing the bias current without the need to adjust RC variables.

主权项

1. A method comprising:
providing a gate driver circuit comprising a rail-to-rail operational amplifier configured to receive a high supply rail voltage and a low supply rail voltage, the operational amplifier having an output stage configured to provide a gate activation signal that is based upon one of the high supply rail voltage or the low supply rail voltage as a supply rail value of the amplifier for switching a selected row of transistors in a display panel, wherein the output stage comprises a compensation capacitance and a current source configured to provide a bias current; and using a programmable slew rate control circuit to adjust a slew rate of the gate activation signal provided by the operational amplifier, wherein adjusting a slew rate of the gate activation signal comprises adjusting the bias current provided by the current source, wherein the current source comprises a programmable current mirror including a reference current system configured to adjust a reference current and a mirror system outputting the bias current mirrored to the adjusted reference current, wherein the reference current system includes at least two transistors arranged in parallel, each of which corresponds to a programmable switch, and wherein adjusting the bias current comprises selectively opening or closing the programmable switches corresponding to the transistors of the reference current system.