By: Dave Johnson
These days, I seem to be
designing a lot of circuits, which run on very low power. Often the resistors
being used in these circuits are in the multiple megaohm order of magnitude.
When looking at signals across such resistors, even the 10M load a typical X10
oscilloscope probe will produce large measurement errors and will influence the
circuit operation. To reduce the effect such a probe has on the circuit, I
reach for my X100 scope probe. My probe, with its 100M impedance, is a
commercially made device but if you want to make one, it is not hard to do.