I'm trying to do some reverse engineering on the NE5532 schematic, but I can't understand how is designed the current source for the first stage. What I want to analyze now is in yellow on the picture. As I understand, the first differential amplifier is polarized with a Widlar current source(Q1-Q3), but what I'd like to know if someone can figure out:

  • The purpose of Q2. Having another widlar source? But why would we need that?
  • The purpose of the active load Q4-Q5 and the transistor Q7. Why the reference transistor Q3 isn't just plugged with a resistor directly to VCC to generate the reference current?
  • What's the purpose of the branch of the JFET (Q6-Q8)?enter image description here
  • \$\begingroup\$ Here you have the early version of this circuit. i.sstatic.net/JGnz3.jpg The Q1, Q2 ,Q4, Q5 are the current mirror + bandgap reference. And Q6, Q8 is a start-up circuits for the bandgap reference. I guess. \$\endgroup\$
    – G36
    Feb 5, 2023 at 18:34


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.