W
Winfield Hill
- Jan 1, 1970
- 0
Ken Smith wrote...
Actually that's a good place to switch to IC technology, such as a
fast opamp. Plus, a BJT often fits better than another JFET for the
input JFET's cascode stage.
Winfield Hill wrote:
[....]The 2sk170 with its under-1nV spot voltage-noise level isn't best
employed in a follower circuit, because this low noise level would
force one to follow the JFET follower with an unusually-low-noise
BJT amplifier, such as one using Rohm's 0.55nV 2sd786 transistors.
That's not appealing, compared to a properly-designed common-source
JFET amplifier that provides all the advantages without the pain.
Yes, an amplifier where the feedback to the source is taken from
much later in the circuit is a better way to go. You usually want
to follow the cascoded pair of JFETs with a low noise PNP stage.
Actually that's a good place to switch to IC technology, such as a
fast opamp. Plus, a BJT often fits better than another JFET for the
input JFET's cascode stage.