A feedforward capacitor, C_ff, is used to improve phase margin and transient response of circuits which have output capacitors with low ESR. Since this capacitor can conduct noise from the output of the circuit directly to the FB node of the IC, a 1-kΩ resistor, R_ff, can be placed in series with Cff. If the ESR zero of the output capacitor is below 200 kHz, no C_ff must be used.

If output voltage is less than 2.5 V, C_ff has little effect, so it can be omitted. If output voltage is greater than 14 V, C_ff must not be used since it introduces too much gain at higher frequencies.