Hi Officer,

I have a question on Type II compensator shown in this document SLVA662 page 4. https://www.ti.com/lit/an/slva662/slva662.pdf?ts=1641427694852&ref_url=https%253A%252F%252Fwww.google.co.kr%252F

it mentions* 'the transfer function is obtained by calculating the impedance offered by the network placed in the **Op-Amp feedback path (Z**f) and dividing it by the upper resistor (R1)'.*

R4 is not part of this transfer function,. Is this because in AC small signal mode, the node highlight in red is equivalent to shorted to ground and R4 shorted out ?

thanks for your help in advance,

*Weilong.*