On Friday, December 14, 2012 4:08:58 PM UTC-8, raypsi wrote:
On Tuesday, November 6, 2012 5:18:14 AM UTC-5, clifford wright wrote:
Has anyone else tried these circuits?
I have built 2 examples, a 9 MHZ AGC controlled amplifier and a 20 dB wideband amp for a noise cancelling system.
BIG problems! The diode string in the source of the FET always biases the J310 OFF.
According to the spec sheet curves:
The j310 gets turned off with a bias of 3.7vdc,
The datasheet for the J310 specifies a pinch-off voltage range
of -2.0 to -6.5V. Completely normal production variation may be
quite different than the spec sheet curve. So it sounds like
Clifford has J310s that have a relatively small pinch-off voltage,
perhaps even out of spec, and the ~2V drop of the diode chain is
biasing the FET off.
Data sheet for the Fairchild parts:
http://www.fairchildsemi.com/ds/J3/J310.pdf
Dana K6JQ