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For those of you that use Advanced Design System (ADS), from this circuit:

enter image description here

Fundamental Frequency for transient simulation tool is set to 1 GHz.

Yet, I'm getting this output:

enter image description here

Main question:

Since this is common drain, VOUT should at most have the same amplitude as VIN. Probably even negative shift, since I didn't change the voltage threshold (I haven't got to tweaking parameters yet). So what's up with the positive DC bias? Why is the amplification significantly less than unity?

Other questions:

  1. Also, what's that Transient Response at the very first cycle of VOUT? Why would a semiconductor have a Transient Response? Is it because of the "inductance" on the drain and source of a MOSFET?

  2. Lastly, why is it that this simulation does not work on very low frequencies? I first started with 1 Hz scale for everything (just change all units from 1 GHz below to 1 Hz). The M1 just acted like a 1kOhm constant resistor.

I also simulated this in the 1 kHz scale (replaced all units from GHz in the pics to kHz, did the same with Fundamental Frequency). This is the output:

enter image description here

Even here, the DC bias is nearly the same and the amplification is much, much less. It also lags by 90°. Why?

I'm starting to think it's either just using the wrong component or there was a set of parameters to fill-in for this component to get this to work.

The continuation of this discussion: Keysight's Advanced Design System users, what's wrong with this simulation - II

Null
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kozner
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    You are simulating at 1GHz!!! The MOSFET is doing nothing at that frequency, its just conducting a bit, The output is due to capacitive coupling gate to source. 1GHz! – user1582568 Feb 16 '16 at 12:45
  • Did you have a look at that mosfets datasheet? Things like turn on relay time and so on? And I am pretty sure it works fine at 1kHz, your expectation is just wrong – PlasmaHH Feb 16 '16 at 12:49
  • @user1582568: I see. So that's why there's a Transient Response. I thought this (GHz) was the fundamental frequency to make the simulation run, seeing that this package is for HF and that I was getting a flat line on VOUT at the Hz range (as stated in 2) – kozner Feb 16 '16 at 12:50
  • @PlasmaHH: I think you should see my second point above. – kozner Feb 16 '16 at 12:51
  • @kozner: Your expectation is just wrong there, your "gain" will probably like 0.3 or something there – PlasmaHH Feb 16 '16 at 12:53
  • @kozner, now we have the real problem. Have you tried a DC op point simulation? What results do you get? – user1582568 Feb 16 '16 at 13:15
  • Don't add new questions after your old one, this is not now SE works. – PlasmaHH Feb 16 '16 at 13:18
  • continuation of the discussion: http://electronics.stackexchange.com/questions/217538/keysights-advanced-design-system-users-whats-wrong-with-this-simulation-ii – kozner Feb 16 '16 at 13:44
  • Keysight's in the EDA tool business? Wonder how many limbs and first born children they want for that... – Matt Young Feb 16 '16 at 14:29

2 Answers2

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If you look at your MOSFET's datasheet page 2 (like @PlasmaHH proposed above).

You'll see that it is not able to work properly at 1 GHz since it's turn-on and turn-off delay times are about tens of ns which obviously waaaay too slow to operate at this frequency. You should try with a component better suited for RF applications (or just decrease your operating frequency).

MaximGi
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\$v_{gs} << 2 (V_{GSQ} - V_{TN})\$

Here your \$v_{gs}\$ is \$3\sin(\theta)\$.

So condition is not holding.....

See Microelectronics by Donald A. Neamen, 4th Edition, chapter 4.1.1 on page 208.

Velvel
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muon pra
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