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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) posted by Scott Frankland on July 1, 2003 at 15:43:22:
Actually the emitter follower is one of the best output stages possible, for several reasons: First, it has a very low intrinsic output impedance. Second, it can be very linear on an absolute basis, because the dynamic change in voltage across the Vbe junction will be a small fraction of the total voltage across the load. Three, an emitter follower will 'bootstrap' most of its non-linear input capacitance or Cbe to reduce the effective capacitance to a much lower value. Four, an emitter follower is very wide bandwidth. Five, the pentode like characteristics of a bipolar transistor buffer the output stage from power supply variations. etc. This also goes for FET's, in general.
However, this is under ideal conditions. To make this possible, you must bias the transistor so that it can operate at or near its best operating point, and you must drive the transistor with a low impedance source, or else you will get distortion from non-linear beta and varying input impedance of the output stage with load impedance changing. Many designs make serious errors in not driving the transistor follower with a low enough impedance.
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Follow Ups
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - john curl 15:59:38 07/01/03 (11)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - mfc 18:58:45 07/01/03 (9)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - kurt s 22:02:39 07/01/03 (8)
- PS - kurt s 22:29:04 07/01/03 (0)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - mfc 22:25:41 07/01/03 (6)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - Scott Frankland 01:43:17 07/02/03 (4)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - mfc 18:34:52 07/02/03 (3)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - Scott Frankland 19:41:37 07/02/03 (2)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - mfc 22:15:08 07/02/03 (1)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - Scott Frankland 23:42:07 07/02/03 (0)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - kurt s 22:33:03 07/01/03 (0)
- Re: I fixed a bias problem in my Mosfet follower (experiment #1 continued) - Scott Frankland 16:39:51 07/01/03 (0)
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