Re: Realizations with transistors and capacitors in an emitter follower

On Mon, 25 Feb 2008 10:07:37 -0800 (PST), "M. Hamed"
<mhs000@xxxxxxxxx> wrote:

Thanks for your replies. As I had mentioned it was apparently too
obvious to you but you can't imagine how much of a mental block that
was to me. It was refreshing to see that my assumptions and
conclusions were close enough. I'll check the circuits you sent. The
ASCII art is not well aligned though (even with a fixed font). I am
working my way from AoE and trying to build and simulate interesting
circuits.

With this same circuit now, I've tried connecting an OpAmp voltage
follower (LM324N) to the output of the emitter follower to make a high
impedance load, then connected the speaker through an output cap to
the OpAmp output. The situation is much improved but slightly
distorted. Feeding that to the simulator again shows that clipping
happen when voltage is above or below a certain level. If that's not a
simulation inaccuracy then I'm guessing the OpAmp can't source or sink
all the current.

The LM324 will current-limit at very low levels, compared to what a
speaker reasonably needs. It's a bad impedance match.

Plus, an LM324 is a terrible audio amp. It has serious crossover
distortion at even 60 Hz, and gets worse as frequency goes up.

John


.

Relevant Pages

  • Re: Realizations with transistors and capacitors in an emitter follower
    ... I'll check the circuits you sent. ... I've tried connecting an OpAmp voltage ... simulation inaccuracy then I'm guessing the OpAmp can't source or sink ... The LM324 will current-limit at very low levels, ...
    (sci.electronics.design)
  • Re: Realizations with transistors and capacitors in an emitter follower
    ... I'll check the circuits you sent. ... I've tried connecting an OpAmp voltage ... follower to the output of the emitter follower to make a high ... simulation inaccuracy then I'm guessing the OpAmp can't source or sink ...
    (sci.electronics.design)
  • Re: op-amps with wide open-loop bandwidth ?
    ... circuits and though analysis of those designs didn't reveal anything ... Under these conditions, an opamp is a programmable device, It performs an almost unlimited number of functions that are very strictly controlled by the input and feedback networks connected around them. ... So, while it is perfectly good to have single active device stages be slapped with overdrive, and use them to obtain a pleasing sound coloration, this is not the way to do such coloration with opamps. ...
    (sci.electronics.design)
  • Re: Opamp problem
    ... If you do not filter the power, your opamp can be affected ... Many circuits that don't work right may be found to be oscillating. ...
    (sci.electronics.basics)