PCB - top view
Loop gain analysis
THD OPS3 22V
THD OPS3 60V
Very sinple (only 6 transistors) IPS board, current feedback, singleton CFP input stage, CFP VAS stage. Why CFP-Madness ?
It came out of one of my prototypes with CFP output stage so all the three stages were CFP (complementary feedback pair).
Very tricky temperature compensation, total thermal balance is held by the one red LED, which in theory should have very similar temco as PN junction of the BJT transistor. Depend on the supply voltage by adding one resistor we can balance the heat dissipation so the whole amplifier will hold nice and steady output offset DC value.
CFP-Madness should be attached to well buffered output stage, triple emitter follower is recommended. One of my favorite IPS boards, simple, good performance on the paper and nice sound, for someone can turn out a bit too bright at the top octave but in this case it depend a lot on output stage used.
Compensation provides ULGF point at 770kHz PM=60deg and GM=17dB.