Miller compensation capacitor sizing
Given;


uncompensated discrete amplifier with closed loop gain of 20 dB , (R1+R2)/R1= 10x
high Q resonance at 5MHz,
~20dB/decade rolloff >10MHz
0dB gain at 50 MHz which becomes the GBW product.


We could compute the open loop gain 


and determine the ω/RC breakpoint for some circuit Req and added Miller C to achieve 0 dB gain 


and then expect 45 deg phase shift at unity gain at GBW/G = 50MHz for phase margin.

example   


if \$a_v=60dB\$ and 1st order = -20dB/decade above 50MHz the breakpoint "at least" must be less than 3 decades lower or 50kHz.  ( if 80 dB then 4 decades lower)
the Req=R29//hFE*R24 + R25
your C1 is then C1=1/(2π f*Req)



There will be tolerances for each transistor GBW in this design which determines the extra margin to reduce breakpoint. In typical BJT Op Amps , the breakpoint is 10Hz. For video Amps not unity stable it may be > 10kHz +

e.g.   The goal is to make the slope 1st order or phase shift &lt;=90 deg at unity gain and eliminate the cascade stage higher order effects at high gain where negative feedback almost shifts into positive feedback "low phase margin"



ref