Abstract: A source driver for an LCD panel includes two gm stages and two output buffers. In a normal operation mode, the first gm stage and the first output buffer establish a unity gain buffer to amplify a positive polarity analog voltage to be a positive polarity output voltage, and the second gm stage and the second output buffer establish a unity gain buffer to amplify a negative polarity analog voltage to be a negative polarity output voltage. In a polarity inversion mode, the second gm stage and the first output buffer establish a unity gain buffer to amplify a positive polarity analog voltage to be a positive polarity output voltage, and the first gm stage and the second output buffer establish a unity gain buffer to amplify a negative polarity analog voltage to be a negative polarity output voltage.

Abstract: A current limiter is connected between a voltage source and the level shifting latch of a level shifter for limiting the driving current for the level shifting latch under a threshold, to thereby reduce the current consumption of the level shifter during logic transition, by which the level shifting latch can be implemented by transistors with shorter channels, thereby downsizing the circuit area of the level shifter. Preferably, the threshold is adjustable for adjusting the output driving capability of the level shifter and speeding up logic transition of the level shifter.

Abstract: A control method is provided to reduce the spring resonance of a voice coil motor when the coil current of the voice coil motor is changed. Each time a total variation for the coil current to be changed is identified and divided into a plurality of step variations applied one by one with a time step equal to one half of the spring resonant period of the voice coil motor. Due to reduction of the spring resonance, the control method speed up the voice coil motor to a steady state. With this control method, a lens focusing system has a shorter focusing time.