Guys please help me on this...
The text says :
“ As the op amp out put at the junction of D1 and D2 is increased in a positive direction op amp supplies current through D2 and R5 . So the voltage drop across R4 is reduced ,allowing it to pull the Q1 base up to the required level while supplying increased base current to Q1.The Q2 is biased OFF when output voltage is at its positive peak at the junction of diodes.”
But as output goes positive D1 is RB and D2 is FB letting the major current(output current + dc bias from Vcc) flows across D2, resulting in turning Q2 more harder..but the text says that Q2 is OFF during when output is positive….how ?? please justify??????
secondly....
What does the author means by the line "allowing it to pull the Q1 base up to the required level while supplying increased base current to Q1”…Which required level he is talking about???
At node B the voltage is 11.7 V ..and at node A it is 11V but it should be two diode drop below the voltage at node D i.e it should be 10.3 V(because 0.7V voltage is getting dropped at BE junction of Q1 and across D1) please explain why i am having a contradictory idea ???
thnx
The text says :
“ As the op amp out put at the junction of D1 and D2 is increased in a positive direction op amp supplies current through D2 and R5 . So the voltage drop across R4 is reduced ,allowing it to pull the Q1 base up to the required level while supplying increased base current to Q1.The Q2 is biased OFF when output voltage is at its positive peak at the junction of diodes.”
But as output goes positive D1 is RB and D2 is FB letting the major current(output current + dc bias from Vcc) flows across D2, resulting in turning Q2 more harder..but the text says that Q2 is OFF during when output is positive….how ?? please justify??????
secondly....
What does the author means by the line "allowing it to pull the Q1 base up to the required level while supplying increased base current to Q1”…Which required level he is talking about???
At node B the voltage is 11.7 V ..and at node A it is 11V but it should be two diode drop below the voltage at node D i.e it should be 10.3 V(because 0.7V voltage is getting dropped at BE junction of Q1 and across D1) please explain why i am having a contradictory idea ???
thnx
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