Complex sentence: Resistor-diode networks and FETs are sometimes used for the nonlinear element, however a traditional solution is to use a thermistor or an ordinary incandescent light bulb; both provide a resistance that increases with temperature as the current through them increases.
Split into simpler sentences: Resistor-diode networks and FETs are sometimes used for the nonlinear element. A traditional solution is to use a thermistor or an ordinary incandescent light bulb; both provide a resistance that increases with temperature as the current through them increases.