With this circuit it is possible to vary the resistance by adjusting the mark/space reaction of the 555. The circuit was found in the November 1989 Radio Electronics magazine.
The gain of the Operational Amplifier in the figure is given by the ratio between R1 and R2. In...
This conventional window comparator configuration was found in an old documentation. It is valid...
This circuit uses a Norton operational amplifier to generate 1 kHz pulses with a 1 to 60...