"Genome" wrote in message
...

"Phil Allison" wrote in message
...

"Genome"

Someone suggested the circuit was crap and asked for an analysis.


** But he was a neo- Nazi TROLL.


I gave an analysis that showed it was crap.


** Shame how that "analysis " was laughable.


The gain equation has been posted & is quite independent

of normal device beta spread - by virtue of local negative feedback.

Now, enjoy the * local negative feedback* YOU are getting.


****WIT !



...... Phil


Gosh, I thought I was quite denigrating of myself when I posted my
original analysis. I even managed to suggest it might be wrong....

Don't suppose you'd like to post the gain equation in response to this one
would you?

Tah.

DNA


Oh, all right then. I went and found it myself.

Fair enough I didn't post a proper analysis of the actual circuit, I'm not
clever enough. Well actually I couldn't be bothered to take it further.
However, I did work out an equation for the gain of your compound
differential pair that seems fairly close to the mark.....

Bpnp = 05 Av = 56.9dB
Bpnp = 10 Av = 60.6dB +3.7dB
Bpnp = 20 Av = 64.4dB +3.8dB
Bpnp = 40 Av = 67.8dB +3.4dB
Bpnp = 80 Av = 70.5dB +2.7dB

That looks, more or less, like the gain depends on Beta in the manner
suggested.

Of course I've not considered the effect of the remaining 22R resistor and
since re @ 1ma is at about 25R that may well reduce the dependence as well
as reducing the maximum achievable gain.

Thanks for explaining stuff.

Cheers

DNA