NPN: BC 546/547/550
PNP: BC 556/557/560
Should all work, the major difference between them is the VCEO and VCBO.
BC 548/549 and BC 558/559 have VCBO and VCEO of only 30V. The others have VCBO and VCEO from 45V to 80V.
I have similar oscillation about 200mV rms 20MHz in my amplifier: Blameless class A with TMC compensation. Oscillation appear if bias current at class A, it is disappear when bias current reduce. After I read this thread, I tried to put RC in emitter VAS buffer. Oscillation gone.
Thank you.
Thank you.
If you are using a beta helper to buffe4 your VAS stage, try just decreasing the emitter resistor of the beta helper - 1k should do it.
I think you may have a different mechanism. If this is the Douglas self one with the differential bias controller, it may be related to the bias control circuit (small signal so can oscillate at HF). Also, might be you have a minor loop instability issue.
Anyway, good that you have fixed it!
Is a development of the sx-Amp and is a better amp. The sx is from 2012 and the kx from 2018
🙂
question
Hi Bonsai. First of all, thank You for sharing schematic of KX amplifier and for all support...I would like to ask You for recommedation, in UBx buffer You used BF892 Jfet transistor, but they are now obsolete, any replacement /except 2KS170BL?
Hi Bonsai. First of all, thank You for sharing schematic of KX amplifier and for all support...I would like to ask You for recommedation, in UBx buffer You used BF892 Jfet transistor, but they are now obsolete, any replacement /except 2KS170BL?
No. The bias controller like Nelson Pass's amplifier in the 80's.
But I still do not understand the mechanism that cause oscillation in my amplifier.
