Based on LM 13700 dual OTA
An OTA is basically an opamp with voltage input and current output.
What makes these so versatile is that the gain (mA per volt) is adjustable
Over a large range by way of the Iabc input which determines the bias
current and thereby the gain of the differential pair of transistors at the input,
the rest of the ota is constructed from 4 current mirrors , giving a bipolarity
output of current that is proportional to the Iabc current and the voltage
difference at the inputs.
