Sample and hold circuitry for monitoring voltages in an implantable neurostimulator

Circuitry for an implantable stimulator device configured to provide a stimulation pulse having at least first and second phases between first and second electrodes, the circuitry comprising: a first capacitor; a second capacitor; and switching circuitry, wherein the switching circuitry is configured to: store a first voltage between the first and second electrodes across the first capacitor during the first pulse phase, store a second voltage between the first and second electrodes across the second capacitor during the second pulse phase, and serially connect the first and second capacitors to produce a sum of the first and second voltage after the second pulse phase. rr r LUj LU - C) LU LU r Ln LUj coo N D' C) ~