On designing OTA-C graphic-equalizers with MOSFET-triode transconductors

A CMOS audio-equalizer based on a parallel-array of 2^nd-order bandpass-sections is presented and realized with triode transconductors. It has a programmable 12 dB-boost/cut on each of its three decode-bands, easily achieved through the linear dependence of g_m on V_DS. In accordance with a 0.8 μm n-well double-metal fabrication process, a range of simulations supports theoretical analysis and circuit performance at different boost/cut scenarios. For V_DD=3.3 V, full-boosting stand-by power consumption is 1.05 mW. THD=-4.261 dB at 1 V_pp and may be improved by balanced structures. Thermal- and 1/f-noise spectral densities are 3.2 μV/Hz¹² and 18.2 μV/Hz¹²@ 20 Hz, respectively, for a dynamic range of 52.3 dB at 1 V_pp. The equalizer effective area is 2.4 mm². The drawback of the existing transmission-zero due to the feedthrough-capacitance of a triode input-device is also addressed. The proposed topology can be extended to the design of more complex graphic-equalizers and hearing-aids