Fully-integrated 5 to 15 MHz programmable bipolar Bessel lowpass filter

Design and experimental verification of a fully differential monolithic bipolar seventh-order Bessel lowpass filter are presented. The transconductance-C filter is unique in its dual emphasis on magnitude and constant group delay characteristics. Its pole frequency f_c is current tunable between 5 and 15 MHz. The circuit also incorporates user programmable equalization. Measured group delay variation with and without equalization is less than 1 ns between DC and 1.5 f_c. With 5-V operation and 2-V_pp input signal, the total harmonic distortion is less than 1%. The filter is primarily targeted at high-performance disk drives and constant density recording applications. Its design generality and excellent high-frequency performance show great promise for other future applications, potentially up to 100 MHz