Abstract: An overvoltage-tolerant self-biasing input/output buffer circuit having a p-channel field-effect transistor ("FET"), a first n-channel FET and a biasing circuit for biasing the body of the p-channel FET so as to prevent forward-biasing of the of the p-channel FET. The p-channel FET has a source connected to a first voltage, a gate connected to a first input, a drain connected to an output, and the body connected to a node. The first n-channel FET has a drain connected to the output, a gate connected to a second input, a body connected to a second voltage, and a source connected to the second voltage. The biasing circuit includes a second n-channel FET and a third n-channel FET. The second n-channel FET has a source and a gate connected to the first voltage, a drain connected to the node, and a body connected to the second voltage. The third n-channel FET has a drain connected to the node, a gate and a source connected to the output, and a body connected to the second voltage.

Abstract: An ion energy filter of the type useful in connection with secondary ion mass spectrometry is disclosed. The filter is composed of a stack of 20 thin metal plates, each plate being insulated from the others and having a centrally located hole with a unique radius. A metallic hemisphere is mounted on a base plate, and the 20 thin metal plates are attached to the base plate such that the plate with the smallest central hole is adjacent to the base plate and the radii of the holes in subsequent plates increase with increasing distance from the base plate. The relative potential of each plate is determined by a series string of 20 resistors with each plate being connected to a different junction in the series string. The radii of the centrally located holes are selected such that the voltage on each plate is inversely proportional to the radius of its centrally located hole.