# Electric OU: Tar Baby and Tex (the Tektronix DSO) Go On Another Play Date

The Tektronix DSO’s math functions are used to demonstrate the negative mean power product in two ways: the raw mean and “mean of means” is computed for the math trace, and also the Areas under the math trace curve lobes are computed. A negative mean power product is shown and also the area result is negative, meaning that an integration would result in a decreasing sum or a negative energy product. Tar Baby is running here with a Negative DC bias produced using the 55 charge pump inverter circuit and the main running batteries; no eternal bias source is used. The decouple/filter caps are about 11 uF of snappy poly caps and monolithics in combination and produce just enough smoothing of the battery trace to flip the sign of the scope’s computed mean power. If I’d hooked in the 250 uF cans, the smoothing would have been even better, but even just with the 11 uF it was enough to “rationalize” the power product. I forgot I had the 250 uF cans in the bag so I didn’t even take them out. Traces: Top, yellow, trace #1 is the voltage across the Current Viewing Resistor, equivalent to the current flowing through that resistor, a 0.2 ohm 3-watt commercial CVR (NOT the power resistors used by Ainslie or earlier versions of Tar Baby.) This trace is displayed at 0.5 volts per division and is DC coupled with full bandwidth. Next, Purple, Trace #3 is the “Battery” trace, measured at the + power entry point on the board. 50 v/div, DC coupled, full bandwidth. Next, the RED Math trace **…**