[Eeyore]

Trevor Wilson wrote:

"Arny Krueger" wrote


For one thing, modern output transistors have Ft up in the megahertz
range. Back in the 70s people were still struggling with output devices
with Ft in the KHz range.

**Nope. The Japanese had a goodly number of complementary devices, with
decent Voltage, current and SOA ratings which extended well into the tens of
MHz. By 1974, Hi-Rel had true Triple Diffused, TO3 devices with a 20MHz fT
and 20 Amps capacity.

Hi-Rel ?


Exceptionally linear and very potent devices. I recall
them vividly, since Motorola had announced their intention to commit to
Epitaxial Base devices (ca. 2MHz), since it was impossible to produce Triple
Diffused devices (according to Motorola). Other manufacturers also had some
impressive devices back then. The Marantz 2325 receiver used 2SA747/2SC1116
devices. These posessed an fT of 15MHz.

I recall being impressed by Sanken devices the first time I was designing a
serious amplifier around 1980. I settled for Hitachi lateral mosfets instead.
Obtainability was a serious issue back then.


Having said all that, good gain linearity over a wide current range has only
been a relatively recent development.

With modern low-Z driver stages, current gain linearity is no longer an issue
the way it was.

Graham