Tunable active band-pass filter - has range changed using variable resistor and resistor network connected to its integrators and includes inverter

摘要

The bandpass filter consists of three operational amplifiers. Two are designed as integrators(20, 30) and accordingly have capacitors(C1, C2) whilst the third is designed as an inverter(10) and accordingly has a feedback resistor (14). The frequency of this filter is determined by two resistors(R1, R2). The first is connected between the output of the inverter and the input of one integrator, and the second between the output of one integrator and the input of the second integrator. The first resistor(R1) is a resistor network with given ratios(L:1.618) between its resistors. The second resistor(R2) is a variable resistor, to allow range of the filter the be changed over. The ratio between one setting of the variable resistor and the resistor network is 1:1.272.