S
Stretto
The following is a simple JFET source follower amplifier:
http://imageshack.us/photo/my-images/220/jfetsourcefollower.png/
Every combination of the switches work as expected. When I mock up this
circuit it does not work for direct coupling to any degree like the
simulation. The main issue is when the low side of the AC source is
connected to VDD. In this case I'd expect the DC bias point to be 5V. When
it is instead grounded the DC bias point depends on the R2, R3, and R4.
Choosing R4 << R3 = R2 sets the bias point at 2.5V which can be remedied by
using Vdd = 10V.
The real question is why does my source no behave like the simulation. I'm
using the output of the sound card and cannot "lift" it's ground to work in
any significant way. (I guess the sound cards output is capacitively coupled
but that should then not change anything.
What I'd like to do is direct couple a jfet source follower with output bias
Vcc/2. While I don't have any problem getting this in simulation I can't get
my circuit to work(works find using capacitive coupling).
The only thing I can think of is that it has something to do with the source
circuit itself. It's not passing the DC like it does in the simulation.
Any ideas?
http://imageshack.us/photo/my-images/220/jfetsourcefollower.png/
Every combination of the switches work as expected. When I mock up this
circuit it does not work for direct coupling to any degree like the
simulation. The main issue is when the low side of the AC source is
connected to VDD. In this case I'd expect the DC bias point to be 5V. When
it is instead grounded the DC bias point depends on the R2, R3, and R4.
Choosing R4 << R3 = R2 sets the bias point at 2.5V which can be remedied by
using Vdd = 10V.
The real question is why does my source no behave like the simulation. I'm
using the output of the sound card and cannot "lift" it's ground to work in
any significant way. (I guess the sound cards output is capacitively coupled
but that should then not change anything.
What I'd like to do is direct couple a jfet source follower with output bias
Vcc/2. While I don't have any problem getting this in simulation I can't get
my circuit to work(works find using capacitive coupling).
The only thing I can think of is that it has something to do with the source
circuit itself. It's not passing the DC like it does in the simulation.
Any ideas?