After a lot of theoretical studying of MOSFETs, I decided to try out at least the basics of it in practice.
Here is the first circuit I ever made using MOSFET:
I haven't used resistor in series with gate, because MOSFET is obviously voltage driven component (input gate current is negligible).
I chosen next parameters for the circuit:
- Id(sat) = 10mA
- Id(bias) = 5mA; where Vds = 5V
- Vr1 = 5V
- Rd = Vr1/Id(bias)
Then I didn't really knew which way to calculate Vgs (since the actual gate current can't be really calculated), so I tried next:
- gm = Id/Vds, then Vgs = Id/gm = 5V,
After I made the circuit on breadboard, this are the values I got with measurement:
- if Vgs = 1.8V or less, then Vds = Vcc
- if Vgs = 2.4V, then Vds = Vcc/2 (I wasn't even close to this value...)
- if Vgs = 3.8V or more, then Vds = 0
Where did I go wrong on this one?