Integration of analog filters in a bipolar process

Monolithic analog filters are described which are based on the integration of electronic transconductors and capacitors. The method used allows simulation of inductor capacitor filters. The transconductors are voltage-controlled current sources provided with a scaling multiplier. The value of one external resistor and matching of integrated elements determine the transconductances. Capacitors are made with an oxide/nitride dielectric on the low-ohmic emitter diffusion and with an aluminium top electrode. Applications include PCM low-pass filters, viewdata modem filters, etc. The method is extendable from the audio band up to video frequencies. Simple breadboarding, no need for special CAD, and an extremely low supply power consumption are features of the filter type. The filters are on-chip compatible with analog and digital system parts.