This paper reports results on the use of a pi’n/pin a-SiC:H heterostructure as an active band-pass filter transfer function whose operation depends on the wavelength of the trigger light, on the applied voltage and on the wavelength of the additional optical bias.

Results show that the device combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal. Experimental and simulated results show that the output signal has a strong nonlinear dependence on the light absorption profile. The device, modeled by a simple circuit with variable capacitors and interconnected phototransistors through a resistor, is a current-controlled device. It uses a changing capacitance to control the power delivered to the load acting as a state variable filter circuit. It combines the properties of active high-pass and low-pass filter sections into a capacitive active band-pass filter.