THS3122 The problem with Multisim Simulation

tao lin1

Other Parts Discussed in Thread: THS3122, TINA-TI

I want to simulate a unite feeback circuit,but I found the following problem:
The Input：2Vpp，10MHz sine wave：

My circuit：

When the feedback resistance is 100k(As above),the output is just 120mVpp,far below 2Vpp!

when I change the 100k to 10k, the output is about 1Vpp:

Then change the 10k to 1k, the output is 2Vpp,that is what I want：

I turn to the handbook of THS3122,I found the parameter here:

128-MHz, –3-dBBW(RL=50Ω, RF=470Ω)

1550-V/µsSlewRate(G=2,RL=50Ω)

and I have tried some other OPMAs，and the results are similar,anybody can tell me why?(I think the Multisim Model of THS3122 can't be wrong)

over 12 years ago

0 Hooman Hashemi over 12 years ago

TI__Mastermind 22825 points

Hello Tao,

I believe the reason for the low output transient swing of the THS3122 is because you have chosen high value resistors (100k) with high frequency (10MHz) input. Large value resistors create poles with parasitic capacitances built into the model and limit the response / swing.

Below you see that when I simulate with TINA-TI, I get a similar response where 100kohm output swing is limited but 1kohm swing is 2Vpp, as expected:

So, I recommend you lower your resistor values and try again.

Here is the TINA-TI simulation file for the case above, if you like to experiment with it:

6354.THS3122 low R High R Response Hooman 12_23_13.TSC

Regards,

Hooman

0 Hooman Hashemi over 12 years ago in reply to Hooman Hashemi

TI__Mastermind 22825 points

Hello Tao,

There might have been a problem with E2E on Monday 12/23/13 related to sending out emails with posts.

I just wanted to know if lower resistor values resolve your simulation problem or not?

Regards,

Hooman

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THS3122 The problem with Multisim Simulation