Low-voltage NMOS-based current differencing buffered amplifier and its application to current-mode ladder filter design

An integratable circuit technique to realize a low-voltage current differencing buffered amplifier (CDBA) is introduced. The realization scheme is through the modification of a low-input resistance CCII+ and the proposed CDBA can operate with the minimum supply voltage of +/- 1.25 V. In order that the signal path consists of only NMOS transistors, a negative current mirror using NMOS transistors is employed. With standard 0.5 mu m CMOS process parameters, PSPICE simulation results show that the proposed CDBA provides the terminal resistance of r(n) congruent to r(p) congruent to r(w) congruent to 13 Omega, r(z) congruent to 290 k Omega, and the -3 dB bandwidth of about 500 MHz. Application examples employing the proposed CDBA as active elements in the leapfrog simulation of current-mode ladder filters are also included.