to change the slope of g 2 effectively changing the exponent of the exponentially decaying impulse response when the sensor output is a differential voltage convolutions of the voltage difference v in 1 u2212 v in 2 with decaying exponential functions can be achieved with a similar circuit shown in fig4 b these circuits are very efficient and consume only a fraction of a micro or milli watt when they operate in the subthreshold region if a wall shear stress is measured in terms of the difference between a compressive and a tensile strain using reverse bias piezo tunneling strain sensors implanted on tether arms a circuit is needed to convert the difference in small sensor currents u03b4i i 1 u2212 i 2 to the voltage input required for the convolution integral circuit this current conversion circuit is shown in fig7 and is also designed so it may be integrated as part of the sensor structure on a single chip or module in this design the piezo tunneling junctions which act as strain sensors are connected via a current mirror which feeds the current difference u03b4i to the sense amp block two cascade transistors control the performance of the circuits via the bias voltages v cas 1 and v cas 2.