Bad Circuits


Bad Rumble Filter

This rumble filter is used to improve the output response of motor drivers.

bad rumble filter
bad rumble filter
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In this circuit offset voltages, offset/bias currents saturate the operational amplifier output.
A 100 k resistor connected from output to negative terminal will reduce the effect of bias/offset currents. The problem with offset voltage still remains. Variable resistor offset trimming will reduce offsets. However, variable resistors are not reliable and offset voltage would not affect the output much because the voltage gain will fall due to negative feedback. Therefore offset trimming is not necessary. Negative feedback will improve stability and reduce interference.

rumble filter solution
rumble filter solution
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The modified circuit should be analysed for transient damped oscillations.