I am utilizing the following spice model for a BS170 MOSFET:
*Zetex BS170P Spice Model v1.1 Last Revised 3/5/00
.SUBCKT BS170P 3 4 5
- D G S
M1 3 2 5 5 N3306M
RG 4 2 270
RL 3 5 1.2E8
C1 2 5 28E-12
C2 3 2 3E-12
D1 5 3 N3306D
.MODEL N3306M NMOS VTO=1.824 RS=1.572 RD=1.436 IS=1E-15 KP=.1233
.MODEL N3306D D IS=5E-12 RS=.768
15V, 120Ohm drain resistor, 0.25V input sine, and transient simulation. Bias at 2.5v
I have tried adjusting all the values, with and without the capacitor and so forth. If the DC bias is increased current starts flowing in the FET which decreases the Vout as expected, but at no point does it provide any AC gain.
The DC block, and the AC are outputting as expected. I am not sure how to troubleshoot any further. I am new to ADS so I might be missing something obvious. The parameters for gain are in the model. I did verify it has a transconductance parameter. This MOSFET is a very quick one so 1MHz should be no problem for it. I have an actual working model of it at 14MHz, too.
This has been solved by adding an inductor to the Vbias(gate)