although i'm more or less familiar with tubes, JFET's and BJT's, i keep missing a few things when it comes to comparisons of orders of magnitude and such. so just to get it straight one time, maybe someone could fill me in with that? thanks a lot people :green:
A) what i'm rather sure about:
1. tubes are much more linear than BJT's.
2. tubes and JFET's have higher i/p and o/p Z and a higher dynamic range for i/p voltage
3. linearity of JFET's and tubes is dependent on optimum bias point, where for BJT's is mostly due to negative feedback
4. hierarchy of practical values of open loop voltage gain is BJT > pentode > triode > FET. relating to an amplification factor of 50-500 / 100-150 / 20-60 / 2-50.
5. triodes produce strong 2nd order harmonic, pentodes are more likely to produce 3rd order
6. tubes have a higher corner frequency than BJT's
B) what i'm not sure about:
1. does open loop gain change approx. inversely with distortion? meaning, statement A4 inverted, the hierarchy regarding linearity would be FET > triode > pentode > BJT?
2. somewhere i've read that JFET's are supposed to have a higher dynamic range than tubes i/p wise? which orders of magnitude can JFET's and tubes have for that, w/o NFB applied? for transistors, i read it's only about 1 mV for 1% THD...
3. do JFET's behave like pentodes distortion wise? meaning, they produce strong 3rd order harmonic? where do BJT's come in there?
4. regarding miller capacitance and such, i guess triodes have a higher corner freq than pentodes. what about FET's, and how much lower are BJT's? which orders of magnitudes are we talking about here?
5. what about electron transit times (for BJT's, too?)
of course some of these may be gross generalizations, there may be many exceptions of the rule, but just to get in the ball park. also, i'm aiming about the very propoerties of the components themselves, not about different kinds of circuits they can be used in. meaning no feedback unless mentioned, etc. and no power o/p applications, either.
thanks a bunch people :razz:
A) what i'm rather sure about:
1. tubes are much more linear than BJT's.
2. tubes and JFET's have higher i/p and o/p Z and a higher dynamic range for i/p voltage
3. linearity of JFET's and tubes is dependent on optimum bias point, where for BJT's is mostly due to negative feedback
4. hierarchy of practical values of open loop voltage gain is BJT > pentode > triode > FET. relating to an amplification factor of 50-500 / 100-150 / 20-60 / 2-50.
5. triodes produce strong 2nd order harmonic, pentodes are more likely to produce 3rd order
6. tubes have a higher corner frequency than BJT's
B) what i'm not sure about:
1. does open loop gain change approx. inversely with distortion? meaning, statement A4 inverted, the hierarchy regarding linearity would be FET > triode > pentode > BJT?
2. somewhere i've read that JFET's are supposed to have a higher dynamic range than tubes i/p wise? which orders of magnitude can JFET's and tubes have for that, w/o NFB applied? for transistors, i read it's only about 1 mV for 1% THD...
3. do JFET's behave like pentodes distortion wise? meaning, they produce strong 3rd order harmonic? where do BJT's come in there?
4. regarding miller capacitance and such, i guess triodes have a higher corner freq than pentodes. what about FET's, and how much lower are BJT's? which orders of magnitudes are we talking about here?
5. what about electron transit times (for BJT's, too?)
of course some of these may be gross generalizations, there may be many exceptions of the rule, but just to get in the ball park. also, i'm aiming about the very propoerties of the components themselves, not about different kinds of circuits they can be used in. meaning no feedback unless mentioned, etc. and no power o/p applications, either.
thanks a bunch people :razz: