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In my electronics class we are learning BJT, Mosfet, JFET theory. My gripe at the moment is that when teaching this you are taught how to troubleshoot and solve for circuits already made. This means you are always solving for various voltages, currents, Gm etc etc. With no previous explanation of how We did a lab today where I had 2 design a 3 channel Jfet amplifier using a 2n5459.

I sort of have an idea but I am mostly lost.

This is school work, so don't give me answers just nudge me in the direction.

I know from the data sheet:

VP is -2 to -8V

Idss is 4 Ma - 16 Ma

Gfs - 200 umhos - 600 umhos

I tested my jfet and found my Idss to be 13.46 mA using a test circuit

I also found Vp to be -4.8V

I plotted and graphed a detailed Vgs Vs ID plot.

Other info needed for design of circuit:

- Av 3-4

- Input signal 200mBpk

- Power supply 9V (Can be 12V if needed due to high Idss)

Things I think are correct

- I know that if I make this a voltage divider circuit R1/R2 ratio will have to give me my desired Vp. I also know from seeing circuits these resistances are usually around the 1M ohm area.

- I know that Vds is a value I must choose to try and solve for.

- I I feel like Rs doesn't really change Vout alot but I could be wrong. It would however at to total current flow from Drain to Source.

- I know that Vds must be in the active region, not the ohmic region.

Problems

- I dont know which thing to solve first. I have no intuition of where to start because Im not really 100% sure how R1/R2 (Zin) affect Zout or any sense of order because I've never had to think of it this way.

- I've tried analyzing it as DC, as the small signal model used for AC analysis, and as the graphed parameters.

- Can anyone explain or help me get started? The only thing I have figured out is that I can solve GM. I'm not sure which variables are things I choose, how to pick a number for R1/R2 or how to even manage to find values with Av needed.

Thanks in advance.

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# JFET, Mosfet, BJT Design Question

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