2181 Blackmer® Voltage-Controlled Amplifier ICs THAT Corporation 2181 Blackmer® Voltage-Controlled Amplifier ICs are high-performance current-in/current-out devices. The ICs feature two opposing polarity, voltage-sensitive control ports, and offer wide-range exponential control of gain and attenuation with low signal distortion. The parts are selected after packaging based primarily on after-trim THD and control-voltage feedthrough performance.