J
James Meyer
- Jan 1, 1970
- 0
James Meyer wrote:
(snip)
I played around with the simulator, last night, and was able to get a
voltage gain of about 2 with the 2N3904 common emitter at 40 MHz with
an source impedance about twice the collector resistor. Pretty lame.
But I did a bit better (more than 4) with a cascode arrangement. I
may try to see what I can do with an emitter follower on input and
output (4 transistors, total). The low input impedance of the common
emitter stage at 40 MHz is what really bites when you are trying to
get both voltage and current gain, unless you can tune the capacitance
out with inductance, but then you get a narrow band amplifier and a
big tendency to oscillate.
(snip)
The simulation is unrealistic in another way too. The input signal
generator with its 50 ohm internal impedance is coupled directly to the input
transistor's base with a cap. That supplies the base with unreasonably high
currents. In the real world where the antenna supplies current to the LC
network, the relatively low input impedance will suck up all the current leaving
precious little voltage at the input.
Jim