Hi ! sorry for my basic question
I would be very grateful to get a kind advice about how to select bjts to be used in line preamp and line level buffers
I am playing with LTSpice I say playing because i just try different values and voltages without really understand what i am doing
Anyway i have noticed a certain change in THD performance changing bjt Strangely some smd parts seem to perform better than three legs parts
Are there better parts for a same purpose ? what i have to look in a datasheet ?
Thank you all very much indeed
I would be very grateful to get a kind advice about how to select bjts to be used in line preamp and line level buffers
I am playing with LTSpice I say playing because i just try different values and voltages without really understand what i am doing
Anyway i have noticed a certain change in THD performance changing bjt Strangely some smd parts seem to perform better than three legs parts
Are there better parts for a same purpose ? what i have to look in a datasheet ?
Thank you all very much indeed
Distortion is probably mostly to do with hfe and Early effect, plus base-collector capacitance. And of course the noise parameters of the transistor may be important depending on the level of signal.
You could try KSA992 and KSC1845, which handle high voltage too as well as being cheap available signal transistors with good specs.
Personally I pick the transistors that come in an opamp input stage(!) for line level stuff, matched pair comes as standard...
And remember many Spice models don't model the faults of real devices very well, so you may be getting a rose-tinted view of the real devices.
You could try KSA992 and KSC1845, which handle high voltage too as well as being cheap available signal transistors with good specs.
Personally I pick the transistors that come in an opamp input stage(!) for line level stuff, matched pair comes as standard...
And remember many Spice models don't model the faults of real devices very well, so you may be getting a rose-tinted view of the real devices.
hi thank you very much for your kind and valuable advice
i am at the start and i am getting info I have already noticed that higher voltages tend to lower the THD at least in simulation
I am focusing very simple circuits for buffers and low gain line stages I think i could a low noise npn and pnp pair for the input and an output pair able to dissipate around 1W I have seen some schematic from commercial amps but i have to find the models and understand how to add them at the Spice default library
I will look also at the Mouser catalogue I read that Toshiba parts are quite good
and also i saw MJE172 and 182 used as output pair in a Bryston discrete opamp used in their top of the line preamps and as drivers in power amps
For buffer i like the diamond buffer I understand that even if simple it can be very effective
i am at the start and i am getting info I have already noticed that higher voltages tend to lower the THD at least in simulation
I am focusing very simple circuits for buffers and low gain line stages I think i could a low noise npn and pnp pair for the input and an output pair able to dissipate around 1W I have seen some schematic from commercial amps but i have to find the models and understand how to add them at the Spice default library
I will look also at the Mouser catalogue I read that Toshiba parts are quite good
and also i saw MJE172 and 182 used as output pair in a Bryston discrete opamp used in their top of the line preamps and as drivers in power amps
For buffer i like the diamond buffer I understand that even if simple it can be very effective