Amplifier

[hmountass]

Hello,
I'm trying to simulate an ultra-low voltage amplifier from ALD company, but I can't find the parameters required for the simulation in ADS or Qucsstudio. Despite thoroughly reading the datasheet, I was unable to find the specific information I need. My voltage supply for the simulation is set at 0.25 V. I wonder if someone has used ALD110800/ALD110900 for simulation in ADS or if anyone has the SPICE model of those transistors. The circuit that I'm trying to simulate is this:

 

[BradtheRad]

It's for real. These devices are remarkable, operating at very low volt levels.

Quotes from data sheet:

an input amplifier stage operating at 0.2V supply voltage has been demonstrated.

The VGS(th) of these devices is set at +0.00V, which classifies them as both enhancement mode and depletion mode devices.

--------------------------------------------
To simulate it should be feasible to use a JFET and set threshold voltage to be close to 0V.

Try above and below zero V.
Try both N and P type.

 

[FvM]

Datasheet has characteristic curves and Id equations, no problem to setup a basic SPICE model.

 

[hmountass]

It's for real. These devices are remarkable, operating at very low volt levels.

Quotes from data sheet:



--------------------------------------------
To simulate it should be feasible to use a JFET and set threshold voltage to be close to 0V.

Try above and below zero V.
Try both N and P type.

I tried using JFET transistors and injected a sinusoidal signal with an amplitude of 10 mV. However, I obtained an output of 10e-4 V with an offset of 0.135 V. I'm not sure why this is happening. In my simulation, I used U1 and U2 as P-type transistors.

I also attempted using a different model, but I consistently obtained the same result.
I tried this model also.
.subckt 110800 1 2 3 4 5 params: vtn=-0.037
m1 1 2 3 4 ncg l=7.8e-6 w=138e-6 as=0.603e-8 ps=0.478e-3 ad=0.161e-8
+ nrd=0.3 nrs=1 nrg=25 nrb=35
.param vtx={vtn} cox=1.0 ires=0.41 pox=1.0 M=1
.model ncg nmos (level=1
+ gamma=0.035 lot/4/uniform=-.22 dev/uniform=.04
+ vto={vtn} lot/2/uniform=.2 dev/uniform=19e-3
+ Uo=650 lot/3/uniform=40 dev/uniform=5
+ Ucrit=0.7e4 Uexp=.1 Vmax=1.6e5
+ phi=0.65 tpg=+1
+ nsub={1e16*ires} neff={10*ires} nss=0.7e11 nfs=4.4e11
+ tox=(0.055u*cox) lot/8/uniform=9.1% dev/uniform=.05%
+ Cgso={.94n*cox} Cgdo={.59n*cox} Cgbo={.138n*pox} Xqc=.42
+ cj=.39m cjsw=264p xj=1.0u
+ ld=0.8u lot/uniform=.19 dev/uniform=.02
+ wd=1.05u lot/uniform=.42 dev/uniform=.1
+ pb=.9 js=20e-6 mj=.5 mjsw=0.18
+ kf=.75e-28 rsh=10 lot/1/uniform=4 dev/uniform=.5)
dbv 4 5 dps 0.8e-8
dbd 4 1 dps 0.8e-8
dbs 4 3 dps 0.8e-8
dbg 4 2 dps 0.8e-8
dgv 2 5 dps 0.8e-8
.model dps D (Is=2.61e-7
+ Isr=1.0e-5
+ Bv=34 Ibv=1e+4
+ Rs=2.74e-7 trs1=3e-3
+ Cjo=1.3e-4 )
.ends

 

[BradtheRad]

Running a simulation, Mosfet thresholds set to 0V.

I found it necessary to set a negative supply rail (which is conventional practice for op amps).

 

[hmountass]

Running a simulation, Mosfet thresholds set to 0V.

I found it necessary to set a negative supply rail (which is conventional practice for op amps).

View attachment 183848

Thank you so much, you made my day !
May I ask what transistor you used for this simulation ?

 

[BradtheRad]

I'm using Falstad's animated interactive simulator.

The mosfet model appears to be generic. Its edit window has only a few parameters which are user-changeable.

https://tinyurl.com/2hzojxfd

By clicking the above link:

1) Navigates to website: Falstad.com/circuit

2) Loads my schematic into the simulator

3) Runs it on your computer.

Right-click on a component and select Edit to change its value.

--- Updated Jul 13, 2023 ---

Select Toggle Full Screen from the File menu.

To increase height of scope traces, hover mouse on the border between circuit and scope traces. When a blue line appears, click it to lift blue line where desired.

 

[hmountass]

I'm using Falstad's animated interactive simulator.

The mosfet model appears to be generic. Its edit window has only a few parameters which are user-changeable.

https://tinyurl.com/2hzojxfd

By clicking the above link:

1) Navigates to website: Falstad.com/circuit

2) Loads my schematic into the simulator

3) Runs it on your computer.

Right-click on a component and select Edit to change its value.

--- Updated Jul 13, 2023 ---

Select Toggle Full Screen from the File menu.

To increase height of scope traces, hover mouse on the border between circuit and scope traces. When a blue line appears, click it to lift blue line where desired.

Hello! Thank you very much for your help!
I may have another question. I simulated my circuit with an input voltage of 30 µV and a supply voltage of 0.25 V. However, at the output of my system, I'm getting an amplified signal with an offset. I want to know where this offset is coming from and if it's normal to have it, or if my circuit is not functioning properly.
Here is my input and output signals

 

[BradtheRad]

Methods to shift output waveform downward:

* Increase resistance in upper section of amplifier.

* Reduce resistance of lower section.

* Use potentiometer to adjust bias so transistor turns on more to reduce resistance in path to ground.

* Create negative voltage at bottom supply rail.