NCS2006 AOP LTspice open loop simualtion got wrong

[Ninja13]

Hello,
I have been trying to simulate the NCS2006 AOP open loop gain to check the simulation model but it seems it gone wrong.
Can you please take a look at botom data and tell me if I did something wrong or if the simulation is just simply wrong itself ?

First, specification of NCS2006:

• It can be seen that Gain unity frequency is 3 MHz (Gain bandwith product is 3.10^6)
• Typical pen loop gain is 120 dB

We can deduce the corner frequency which is 3 Hz.

Secondly, the simulation: I have taken the simulation model on OnSemi web site (here)and simulate an open loop frequency response simulation using different method of open loop simulation strucutre and each time, I don't get the above datas.

First method:

which is not the frequency response expected at all..

Second method:

Not same result but still wrong...

Third method:

4th method:

so.. all of theses methods give results with does not corresponds to the datasheet specification..

 

[Dominik Przyborowski]

What is an ICMR specification for this opamp?

 

[Ninja13]

Hello Dominik Przyborowski,
I am not really sure about the meaning of ICMR, but:

• the common mode input capacitance is : C_cm = 5pF
• the common mode input resistance is: R_in = 10 GOhm

I hope it will help you, to help me =)

 

[KlausST]

Hi,

I am not really sure about the meaning of ICMR, but:

why not doing an internet search "what is OPAMP ICMR" ?

Klaus

 

[Ninja13]

Hi KlausST,
Ok, now I see what it is (sorry, english is not my native langage and the first google reseach I have made about ICMR didn't give me anything)
The ICMR of the NCS2006 is [Vss - 0.2 V ; Vdd+0.2V]

--- Updated May 25, 2021 ---

 

[Dominik Przyborowski]

Read data sheet carefully. It mentions 120dB and 3MHz for 5.5V supply and 5.5k load resistance. You can't expect the same value with half of this supply and lower resistance.
Check also notes of model (if any are provided).

 

[FvM]

ICMR including GND is nice, but the output voltage range range surely doesn't include GND.

As far as I see, the output is biased at GND by all test circuits which can't work. I presume you don't have a hidden DC bias source.

Please correct and come back.

 

[Audioguru]

Ninja, your opamps have a single positive supply but their +input is biased at 0V so the opamps do not work.

 

[FvM]

Use e.g. first method and add 0.5 V DC to V2, biasing the output to 1V.

 

[Ninja13]

Thanks everybody,

It works by just adding a 0.5V DC to V2, but, despite your explanations (@Audioguru and @FvM), I do not understand why it is needed..
Could you please exprain a bit more ? or maybe have a specific linked related to this issue ?

I see that the opamp has a single supply and V+ is biased at 0V.. is it something related to that V- or Vout which would be out of the admissible range of the opamp and then it would saturate, which can not be used for an open loop simulation ?

Thank you in advance,

 

[crutschow]

It works by just adding a 0.5V DC to V2, but, despite your explanations (@Audioguru and @FvM), I do not understand why it is needed..

The op amp has to have a DC bias within its normal AC linear operating range.
0V is not in that range.

The 4th method is the only one I see that will give the open-loop response.

 

[Dominik Przyborowski]

I see that the opamp has a single supply and V+ is biased at 0V.. is it something related to that V- or Vout which would be out of the admissible range of the opamp and then it would saturate, which can not be used for an open loop simulation ?

What you usually see is "small signal ground".

 

[crutschow]

What you usually see is "small signal ground".

In this case the large signal and small signal grounds are the same.