Power efficient output stage for high density implantable stimulators

In implantable stimulators, a current-controlled stimulation is preferred over a voltage-controlled one due to its safety. However, the power efficiency is a major disadvantage. By reducing the headroom voltage needed in the current driver, power efficiency of a constant current stimulation is improved. A promising technique is to bias the transistor in the triode region whereby improving output impedance through the regulated cascode structure. This comes with a feature of an implicit compliance monitor. Proposed is a new power efficient high compliance output stage.