someone can help me to analyze this circuit?

Thread Starter


Joined Apr 16, 2011
Hi everyone!

Someone can help me to analyze this circuit? It is a circuit of a power amplifier.
This amplifier has already been assembled and I know that it works.
Q13, Q15, D6, D7, R18 and R21 form two voltage stabilizers feeding U1.
Q12, Q14, D5, D8, R16, R17, R19 and R20 form two current sources.
Q11, R14, R15, R16 form a vbe multiplier.
Q1, Q2, D1, D2, D3, D4, C1, C2, R1, R2, R3, R4 form a VI limiter.
Q3 and Q7 are predrivers.
Q4, Q5, Q6, Q8, Q9 and Q10 are output drivers.(2SC5200 and 2SA1943)
U1 (tl071) is the input stage.
All right so far?
I don't understand how the op amp drivers the output stage and how the local feedback of the op amp works and how
the global feedback (feedback between output and the op amp) works.
I thought the voltage amplifier was the op amp, but the signal level at pin 6 (output) is much smaller than the signal level that drivers the predrivers.
The VI limiter it's ok? If not, someone can help me to correct? The source is +40V and -40V and the load is 4ohms.
What is the maximum power that this circuit can achieve with a load of 4ohms and what source?
This circuit can work with a load of 2ohms? Under what conditions?
I'll be very grateful to anyone who can help me.