RadioBanter - View Single Post

August 9th 05, 10:08 PM

On 9 Aug 2005 13:10:53 -0700, wrote:

Tom and Allison,

Thanks for your replies. The reason I'm asking is that I built two
class A small signal VHF stages using 2N3866's, powered by 14 volts,
and I'm getting only 2 to 3 dB gain per stage. Then, I was told to
change the transistors to 2N4427, which are 12 volt devices. Would the
gain improve by changing to 2N4427's? Please explain saturation
voltage. Thanks,

C.W.

Thats horrid performance. I've used 2N3866 at 144mhz and seen far
better gains than that at 12V.

What you don't specify is the (ther than VHF) is the frequency in
use. A transistor with an Ft of 500mhz at 250mhz is going to exhibit
poor gain.

A better choice would be a 2n5179, characterized for lower voltages
and has a hight Ft. I've also used 2n5109 at 440mhz/12V with good
gain, thats what 1200mhz Ft buys you.

FYI: saturation voltage is the votages measured from collector to
ground(usually same potential as emitter) at some specified current
with the device turned on hard (over driven). Applies to switching
circuits usually.

Allison