|
Common Source single stage amplifying Mosfet in the Saturation state.
Disconnect both the input cap to divider and the output cap at the drain in order to set up the initial d.c. Q
Then re-connect them for final view. Do that after every alteration on EC to ensure that changes update correctly.
10v Vgs 1/3 Vdd bias divider resistors high impedance
15v Vds half of Vdd as Q
0.081A at Q half of Id max as per Rd= 162mA by V=IR
Kn = KP = 1mA/V² set when (W/L) =2
gm= 2 Id/Vov = 0.162/(10-1) = 0.018 gm is transconductance, Vov is an easier way of writing (Vgs-Vth)
gm x Rd = 0.018 x 185 = 3.33 Amplitude = (gm x Rd) it shows Vout/Vin then multiply that by input.
3.33 x 100mV input = 333mV output peak ...as seen approx. on EC scope.
Caps not yet adjusted for 20Hz -3dB ... C=[1/(2pi x 20 x R)] where R= (r1 x r2)/( r1 + r2) bias res. C=95.5nF?
Note...bias for Q 10v gate Vg is reasonable as rule of thumb 1/3 Vdd .... it can be adjusted.
15v Q drain as set d.c. volts is reasonable for V swing on drain from superimposed input Vgs,
81mA Q reasonable for d.c. current for the swing on drain from Vg a.c. input at 100mV. keep input low.
rms, dB & power not considered here for clarity at this point. eg. datasheet power diss. ...Id is high here.
...open to discussion on this topic....most EC users are likely to know a lot more than me about amplifiers,
but hopefully some users who were not too familiar with Mosfets may have picked up a few tips here.
You might want to put a Rs and perhaps try a cap across it....if so remember to rethink the Vgs value etc. ie Vgs=Vg-Vs but you will need to use that Vs value ....likewise with the Vds=Vd-Vs
Earlier part 6 here http://everycircuit.com/circuit/4940688430202880 ... remember the footnote there.
Or, for the more commonly used (and for me preferred) mosfet state of full switching in the Ohmic state, then use the quick setup as in part 3 here: http://everycircuit.com/circuit/6179495276183552 . This Ohmic state is called 'Linear' by most users, but be aware that some confused users call the Saturation state Linear due to the straight horizontal line seen in the Saturation graph of Ids vs Vds
Being more reliant on the Vds, the formula for Id in the Ohmic state is different to that of the Saturation state.
( See here for Ohmic articles: http://everycircuit.com/circuit/6063244598050816 )
Further Mosfet analysis .... 'join the Q' here: http://everycircuit.com/circuit/6347349325774848
Rds₍ₒₙ₎ and heatsink help .... http://everycircuit.com/circuit/5362558166106112
|
