A REALIZATION OF LOW SENSITIVITY RCCS-CONTROLLED MONOLITHIC INTEGRATORS AND THEIR APPLICATION TO RC ACTIVE-FILTERS

Up to present, some automatically tunable active RC filters have been proposed for the monolithic integrated continuous-time filters. In this paper a synthesis method of monolithic active RC filters is presented, whose characteristic is hardly dependent on temperature, supply voltage and so on, theoretically. First, this paper describes a variable integrator controlled by bias current. Second, a resistor controlled current source circuit (RCCS) is also proposed, which contains the voltage controlled current source (VCCS) being identical with that used in the realization of the integrator and whose current is controlled by an external resistor. The use of this VCCS in the RCCS can completely compensate the variation of the integrator characteristics. Finally, these circuits are applied to realize a third-order elliptic low-pass filter, which is simulated on PSPICE. From the simulations, we obtain excellent results as follows: The deviation of gains in the passband due to the variation of temperature with a range of -10-degrees-C to 60-degrees-C is within +/-0.02 dB; A total harmonic distortion with a 1 V(p-p) input voltage at 100 kHz is less than 0.4% when the cut-off frequency is 1 MHz and the supply voltage is 5 V.