[ExI] Electronic Circuit Question

[Jef Allbright]

On Sat, Mar 1, 2008 at 8:08 PM, Lee Corbin <lcorbin at rawbw.com> wrote:
> Yeah, this is pretty off-topic, and I do apologize to the list.
>  But it was a quiet Saturday afternoon, and I thought it might
>  provide some interest---besides, I was getting damn sick
>  staring at the circuit diagram.  :-)
>
>  Jef writes
>
>  > You didn't mention the value of the load impedance,
>
>  It didn't say. The circuit is supposed to have high output impedance,
>  so I thought it wouldn't matter---and I'm pretty sure that that's what
>  the authors are trying to communicate.

The defining characteristic of an emitter-follower circuit is its
**low** output impedance, capable of driving higher-current loads.



>  > but if it were equal to the emitter resistor value, then you would in effect have a
>  > voltage divider putting the emitter at approximately -5V, and (when
>  > the transistor is forward-biased) the base at approximately -4.4.
>
>  Hopefully I have "drawn" the circuit intelligibly for you. A load
>  impedance (load resistor) that you are describing would be
>  parallel to the 1K resistor I described, right? If so, I don't see
>  any voltage divider.

Yes, the load would be in parallel with the emitter resistor, and
ideally of approximately equal value for efficient coupling (energy
transfer.)

- Jef