Re: Early solid state power amps


Barry Mann wrote:
> They are not giving an exact date but Wikipedia claims "late 1960's"
> for the 741
>
> http://en.wikipedia.org/wiki/741_operational_amplifier
>
> Much better reference:
>
> http://smithsonianchips.si.edu/augarten/p18.htm
>
> peggs the 741 in 1968 as a successor to the 709.

That's all very true, but look at the original context in which the
assertion was made:

"When did decent solid state power amps become available?
Were they direct, capacitor or transformer coupled to the load.
Back in the 60's when the first audio amp ICs became available
for battery powered radios and such, the engineers coupled the
output through a transformer! It seemed hard to wean them off
the transformer."

What's the implication here? It's kinda hard to say, but he seems
to be making some connection between transformer coupling and
early audio amp IC's, which have absolutely NOTHING to do with
one another. AC coupling, be it via transformers or capacitors, is
not an artifact of "the first audio amp ICs" but necessitated by the
use of single ended power supplies, resulting is a substantial
DC bias on the output stage. Further, transformers serve the
purpose of allowing matching of disparate source and load
impedances anywhere in a circuit, again, pretty much unrelated
to any notion of the "first audio amp ICs".

And, in the context of his first questions:

"When did decent solid state power amps become available?
Were they direct, capacitor or transformer coupled to the load. "

The answer is before the 1970's, as the examples I showed illustrate,
and, as well, before the use of "audio amp ICs," which really didn't
find
any widespread use until the '70's. Prior to that, solid state
amplifiers
were available in direct, capacitor and transformer coupled designs.

.

Relevant Pages

  • Re: Early solid state power amps
    ... > capacitor or transformer coupled to the load. ... Audio amp ICs in the 60's ?!!! ... Early ss amps were generally single-ended and transformer or capacitor ...
    (rec.audio.tech)
  • Re: Average Current
    ... >> If the load is primarily capacitive, all the rectifier current is ... >> rating required in the transformer. ... voltage across the capacitor. ...
    (sci.electronics.basics)
  • Re: power supply design
    ... As the peak current goes up, not only do you have to worry about the ... in the transformer. ... of the capacitor comes in) limits peak current for you. ... Safe as in protecting the load, or safe as in not catching fire? ...
    (sci.electronics.design)
  • Re: capacitor transformer
    ... >>>capacitors to make a transformer? ... Would changing the ratio of plate ... >>>area and plate seperation from the primary to secondary capacitor plates ...
    (sci.electronics.design)
  • Re: Average Current
    ... > voltage across the capacitor. ... > transformer voltage, ... > transformer windings are heated by the RMS current, a pulse waveform ...
    (sci.electronics.basics)