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Funny problem in simulation with .option gshunt=1.5e-7

 

Hi

I encountered a strange problem, I uploaded the file in Temp. It's a simple circuit using LT6202. If I put in .option gshunt=1.5e-7, you can check current through R2 and R3 is 50mA. But if you delete the .option gshunt=1.5e-7, then current goes down to about 3.5mA as specified on the datasheet of LT6202. This happens on LT1803, but ok with LT1360.

Strange!!! Any explanation on this?
 

Hello,

Adding 6MegOhm resistors from every node to GND will kill practically every circuit, because there are resistors with kOhm to MegOhms inside the subcircuit.

Best regards,
Helmut
 

Ala,

Gshunt should probably be no larger than 1e-10.

Your value (1.5e-7) is a thousand to a million times too large.? Side-effects like the ones you observed should be expected.

Andy
 

I thought this only add to the external circuits, not the inside of the opamp.
 

Thanks guys, I thought this only add to the external circuits, not the inside of the opamp. Now I know. I notice the Ti models don't work as well as the LT models, The LT models don't need to play around with all these.

Thanks

Alan
 

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Now you node better.

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates 
Rayleigh, Essex UK
On 2018-11-18 18:09, alan.revera@... [LTspice] wrote:

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I thought this only add to the external circuits, not the inside of the opamp.
 

Hello Alan,

I just tried again with gshunt to check that it really has been used inside the subcircuit.
I got +25% more supply current even with only gshunt=1e-11.
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The more interesting option is gmin which is much less critical. It's applied across all PN-junctions in a simulation.I often try with gmin=1e-10, if a circuit doesn't converge.

Best regards,
Helmut
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