Effect of Load Current and Input and Output Capacitors of a Linear Voltage Regulator Chip on the Frequency Dependence of the Ripple Rejection Ratio

Abstract

Effect of load current and input and output capacitors on the frequency dependence of the ripple rejection ratio is studied for a classical linear voltage regulator based on an LM317L-N chip. In the absence of external capacitors, ripple rejection decreases with an increase in the load current at different input and output voltages. It is shown that a capacitor connected at the regulator output provides a significant increase in the ripple rejection ratio at frequencies of higher than 200 kHz and a capacitor connected in parallel to the regulating resistor in the feedback circuit provides an increase at frequencies of less than 300 kHz.