OTA Adder (Summer) and OTA Lossy Integrator:
OTA Adder (Summer) : OTA adder is shown in Fig. 41.9 for which the output voltage is given as
where G = 1/R. This circuit is versatile because the resistor R can be replaced by OTA ground resistor circuit shown in Fig. 41.7 to obtain an all-OTA circuit.
More input voltages can be accommodated simply by adding more OTAs at the input, and interchanging the input leads of one of the OTAs at the input side of the adder changes the sign of the corresponding term in the output.
OTA Lossy Integrator : A lossy differential input OTA integrator is shown in Fig. 41.10 whose output voltage is given by the expression
and, again, the resistor R can be replaced by the circuit shown in Fig. 41.7. Removal of resistor results in a lossless integrator.