fala
Full Member level 5
circuitworks 10 help
Hello, I want to understand how this circuit works, it has been taken from National Application note 272- OpAmp Booster design(**broken link removed**). explaination in the document was not enough for me to understand it fully. I actually build this circuit and it works but I need to understand its theory. I understand this far: Q1 & Q2 are voltage dependent current sources and deponding on the output voltage of the opAmp their collector current changes and by drawing current from 1K resistors they impose a Vbe on corresponding Q3 & Q4. Q5 is a constant current source and as article has pointed out it is used to for bias and Q6 I SUPPOSE acts as an emitter follower and Q5 & Q6 will bias push-pull driver Q7&Q8.
now what I don't understand: it is impossible for Q1&Q2 to both be on because if one is on the other reverse biased so only Q3 OR Q4 can be on not both of them. ok when op amp out put is negative and turns on Q1 & Q3 there is no problem because Q3 draws current from 120K resistor but what about opposite when Q2 & Q4 are on then Q3 is supposed to be off so current for Q4 collector comes from where? why the circuit is not symmetrical for positive and negative ?
I will appreciate any idea that helps me to understand it. thank you very much.
Hello, I want to understand how this circuit works, it has been taken from National Application note 272- OpAmp Booster design(**broken link removed**). explaination in the document was not enough for me to understand it fully. I actually build this circuit and it works but I need to understand its theory. I understand this far: Q1 & Q2 are voltage dependent current sources and deponding on the output voltage of the opAmp their collector current changes and by drawing current from 1K resistors they impose a Vbe on corresponding Q3 & Q4. Q5 is a constant current source and as article has pointed out it is used to for bias and Q6 I SUPPOSE acts as an emitter follower and Q5 & Q6 will bias push-pull driver Q7&Q8.
now what I don't understand: it is impossible for Q1&Q2 to both be on because if one is on the other reverse biased so only Q3 OR Q4 can be on not both of them. ok when op amp out put is negative and turns on Q1 & Q3 there is no problem because Q3 draws current from 120K resistor but what about opposite when Q2 & Q4 are on then Q3 is supposed to be off so current for Q4 collector comes from where? why the circuit is not symmetrical for positive and negative ?
I will appreciate any idea that helps me to understand it. thank you very much.