An externally hosted image should be here but it was not working when we last tested it.
Maybe you can help,
On the circuit there is a 2R2 resistor on the source of the fet... WHY? what voltages does it see? which currents flow through it... how would its size be determined, if I change bias etc in the circuit...
From what I see the 100k pot sets up a voltage divider to provide x volts DC on the gate to enable the fet to conduct from drain to source...
The signal in AC is also put to the gate and a small AC portion is added to the Drain which is allready at a potential of 6.45VDC in order to reach the 168mA,DC on the drain resistor.
At the point between the resistor and drain, I can only see how a small fraction of the signal voltage gets here... Does this small bit also flow trough the Drain to source?
How do I calculate voltage/current gain?
Where is the amplification? what am I missing?
Uncle Nelson, how about a low voltage zen headphone tutorial...aimed at the beginner... In the attached circuit the only part that gets realy hot 60+C is the 2W resistor, I used reasonbly small sinks on the fets themselves. So its a very cheap/safe/easy intro into the wonderfull world and sound of Mosfets.
IRF610 is a current amplifier, being controlled by the input AC Vgs.
Based on the amplified current, the voltage gain is achieved
by the resistors of 33 and 2R2--~33/2R2.
In addition, 2R2 works also for a negative feedback.
Based on the amplified current, the voltage gain is achieved
by the resistors of 33 and 2R2--~33/2R2.
In addition, 2R2 works also for a negative feedback.
Curse at the devil over your coffee, and he posts in your thread...
Nelson, if it wasn't for this little amp, I would not believe myself capable of building one of your amps...
I am now a student of your school.
I see some of your circuits do connect to ground there but seems to have some gain setting method through a trimpot over input and output caps.
Actualy I think I'm makeing progress trying to design another version with double the supply voltage etc... to test if I got the fundemental concepts....
PS, if the 2R2 =33R would it mean unity voltage gain?
First goal is to go from 168mA bias to 400mA wich represents 4.8Watt dissipation over the drain resistor of 30R. with 24v supply, I should be looking at 12V on the drain?
No idea what the fet would be dissipateing...I will hide behind a cushion (the only word ohter than fashion to end on -shion). The current circuit suggests it would be less than the Resistor.
Nelson, if it wasn't for this little amp, I would not believe myself capable of building one of your amps...
I am now a student of your school.
I see some of your circuits do connect to ground there but seems to have some gain setting method through a trimpot over input and output caps.
Actualy I think I'm makeing progress trying to design another version with double the supply voltage etc... to test if I got the fundemental concepts....
PS, if the 2R2 =33R would it mean unity voltage gain?
First goal is to go from 168mA bias to 400mA wich represents 4.8Watt dissipation over the drain resistor of 30R. with 24v supply, I should be looking at 12V on the drain?
No idea what the fet would be dissipateing...I will hide behind a cushion (the only word ohter than fashion to end on -shion). The current circuit suggests it would be less than the Resistor.
- Status
- Not open for further replies.