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How to modify SMPS error amplifier small signal transfer function to include BJT?

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treez

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Equation 25, Page 14 of App Note AN-57 gives the small signal transfer function for the error amplifier and modulator of a topswitch-jx based flyback. (this means the error amplifier circuit of fig23 of page 14 of AN-57)…..

AN-57
https://ac-dc.power.com/sites/default/files/product-docs/an57.pdf

We wish to modify it by having a BJT to amplify the opto-transistor current as in fig31, page 25 of AN-47…..

AN-47
https://ac-dc.power.com/sites/default/files/product-docs/an47.pdf

How does this modify the original error amplifier & modulator transfer function given as above in Equation 25, page 14 of AN-57?
…Presumably one simply needs to multiply the transfer function by the gain (hfe) of the BJT?, (which could be anywhere between 100 and 300)
 

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