US Patent 7286012 Operational amplifier circuit with controllable intermediate circuitry set therein

An operational amplifier circuit includes an operational amplifier, an intermediate circuitry, and a control circuitry. The intermediate circuitry is coupled to a load. The operational amplifier is coupled to the intermediate circuitry and drives the load through the intermediate circuitry according to an input signal. The control circuitry is coupled to the intermediate circuitry and controls the intermediate circuitry to adjust an equivalent loading induced by the intermediate circuitry.