Driving method and related apparatus for improving power efficiency of an operational transconductance amplifier

A driving circuit for driving voltage level of an output terminal toward an input voltage, the driving circuit comprising:

• a first circuit comprising a plurality of transistors;
• and
• a second circuit comprising a plurality of transistors, the second circuit being symmetrical to the first circuit, the transistors of the first circuit having a smaller width/length ratio than the corresponding transistors of the second circuit;
• wherein the transistors of the first circuit are turned on for outputting a reference current so that the second circuit outputs a mirror current, which is greater than the reference current, corresponding to the reference current.

A driving method of an operational transconductance amplifier, the operational transconductance amplifier comprising a first current route, a second current route electrically parallel to the first current route and a control transistor serial to both of the first current route and the second current route, both of the first current route and the second current route comprising a plurality of transistors, each of the transistors of the second current route having a largerwidth/length ratio than the corresponding transistors of the first current route, the second current route having a bypass terminal provided to connect to a load;

• said driving method comprising the steps of:
• turning on the control transistor;
• and
• applying an input voltage to one of the transistors of the first current route;
• whereby in initial phase, the bypass terminal provides the load a larger output current than a current on the first current route;
• in stable phase, the bypass terminal provides an output voltage to the load, which is substantially the same as the input voltage.

An operational transconductance amplifier, comprising:

• a first current route having an input terminal;
• a second current route electrically parallel to said first current route and having an output terminal provided to connect a load, wherein a current on said second current route is a predetermined times larger than a current on said first current route;
• and
• a control transistor serial to both of said first current route and said second current path;
• thereby while said control transistor is turned on and an input signal is applied to said input terminal, in initial phase said output terminal provides the load a current which is the predetermined times as much as a current on said first current route and in stable phase provides the load the voltage level of the input signal.