Design Steps

• Choose R2 so that the current flowing through the feedback network is approximately 1 mA.
  
  
  
• Choose R3 to set the output voltage to the desired value.
  
  
  
• Choose a product of output capacitance C_O and equivalent series resistance R_ESR to generate a zero below 10 kHz (lower is generally better). The frequency of the ESR zero is given by:
  
  
  

  R_ESR can be either inherent in the capacitor used or included separately in series with a low-ESR capacitor (as it was in this case).

• An optional feedforward capacitor C_FF across the feedback network provides an additional zero that improves transient response. The value of C_FF is best selected experimentally. Note that C_FF cannot be used on its own to stabilize the loop. This is because the pole and the zero formed by R2, R3, and C_FF are too close to each other in the frequency domain to stabilize the loop over the whole range of output currents.
• An additional capacitor, C1, reduces the initial voltage step response caused by the relatively high value of
  R_ESR. The value of C1 is low compared to C_O and does not significantly affect stability.