amp with single input can't amplify pulse signal,please help me

thanh · 23rd October 2004, 02:33 PM

hi all! this is my circuit and sim

MikeB · 23rd October 2004, 04:30 PM

Hi thanh !

Hmm, what exactly is your problem ?
The overshooting ? Or the uncentered signal ?

The uncentered signal is an issue with sim. Remove temporaly the
inputcouplingcap and the signal is centered. The amplitude seems
correct. While the sim is biasing the circuit, the inputcap gets charged
with 70mv.

The overshooting is an issue with correctly adjusting feedbackcaps.

Ooops, i detected a FATAL problem in your circuit, NEVER take signal
for feedback after outputfilter/coil. This amp will not be very stable.
Take feedback at L3:1 !

A suggestion, try adding RE of 120ohm to the vas-transistor, it might
reduce openloopgain without increasing thd...

Mike

thanh · 26th October 2004, 01:56 PM

thank mikeb very much! I will try to do like your comments

26th October 2004, 01:56 PM	#3
thanh diyAudio Member Join Date: Jan 2004 Location: ho chi minh city	thank mikeb very much! I will try to do like your comments __________________ Justice for Victims of Agent Orange http://www.petitiononline.com/AOVN/Thank all of you!

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23rd October 2004, 04:30 PM	#2
MikeB diyAudio Member Join Date: Apr 2004 Location: Gütersloh	Hi thanh ! Hmm, what exactly is your problem ? The overshooting ? Or the uncentered signal ? The uncentered signal is an issue with sim. Remove temporaly the inputcouplingcap and the signal is centered. The amplitude seems correct. While the sim is biasing the circuit, the inputcap gets charged with 70mv. The overshooting is an issue with correctly adjusting feedbackcaps. Ooops, i detected a FATAL problem in your circuit, NEVER take signal for feedback after outputfilter/coil. This amp will not be very stable. Take feedback at L3:1 ! A suggestion, try adding RE of 120ohm to the vas-transistor, it might reduce openloopgain without increasing thd... Mike