Digitally programmable active-R square wave generator

A digitally programmable active-R square-wave generator circuit is discussed. The circuit uses only two operational amplifiers, two operational transconductance amplifiers, and resistors. The main features of the circuit are the following: it uses only resistors without recourse to any external capacitors. Therefore, it is attractive for monolithic implementation. It can be used with any mini/microcomputer or microprocessor-based system. It is possible to obtain a linear relationship between the control voltage and the frequency of oscillation. Experimental results are presented