Re: How would one use NPN transistors only?
From: Winfield Hill (Winfield_member_at_newsguy.com)
Date: 06/08/04
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Date: 8 Jun 2004 11:15:03 -0700
MikeM wrote...
>
> B wrote:
>
>> I am familiar with the typical amplifier using NPN, and PNP
>> transistors. It just makes good common sense, even to lay people
>> like me.
>>
>> What about amplifiers that use ONLY NPN transistors? How would that
>> work? It may be elementary, but when I am trying to theorize that,
>> it just doesn't make sense to me.
>>
>> There are a few people now building amplifiers with only NPN
>> transistors, and I understand the advantages, but I don't understand
>> how they make it work.
>
> How did they manage when all they had is tubes?
> Tubes are like NPNs; there were no PNP tubes...
In the early Ge transistor days, everything was all PNPs. :>)
In tube days the issue of making multistage dc amplifiers (that's
where one runs into a problem) was handled with fixed-voltage
level shifters, made from resistors, or from neon lights. In
more recent times with early ICs that were NPN only, resistors
were used, both as voltage dividers and with current sinks, as
well as 6V zener diodes (made from reversed-BE junctions).
Examples can be seen in the old uA702, uA709 and uA715 opamps.
Thanks,
- Win
(email: use hill_at_rowland-dot-org for now)
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