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# what are rgbi and rgbd ??

Last post Mon, Jul 23 2012 1:17 AM by Andrew Beckett. 3 replies.
 Started by niranjan1984 09 Jul 2012 10:34 AM. Topic has 3 replies and 2752 views
• #### Mon, Jul 9 2012 10:34 AM

what are rgbi and rgbd ??
 Hello All,   Output parameters of spectre for BSIM4 model lists two resistances rgbi and rgbd. Spectre Manual gives same description for both of them,'Gate Bias dependent resistance'. I am not sure what these resistance are? are thse Gate resistances? Please clarify. Thanks
• Post Points: 20
• #### Tue, Jul 10 2012 1:26 AM

Re: what are rgbi and rgbd ??
 The documentation doesn't give the same description (at least not in the MMSIM11.1 docs; I didn't look in older versions). rgbi is the Gate Bias-independent resistance, and rgbd is the Gate Bias-dependent resistance. There is a link to the relevant equation for the rgbd parameter. Note that rgbi is an "Output Parameter" - it's purely a function of the input parameters, whereas rgbd is an "Operating Point Parameter", since it's a function of the bias too (as the name suggests).Andrew.
• Post Points: 20
• #### Tue, Jul 10 2012 8:42 AM

Re: what are rgbi and rgbd ??
 Thanks Andrew. I dont see the link which gives the equationf for rgbi and rgbd (I checked Spectre Circuit Simulator Device Model equation manual, probably I have old one). I just want to confirm with you following things1. rgbi is nothing but Rgeltd (bias independent gate resistance) described in BSIM4 manual and is given by                                                    Rgeltd= ( RSHG.(XGW+Weff/3*NGCON)) /NGCON*(Ldrawn-XGL)*NF2. rgbd is nothing but Intrinsic Input Resistance (IIR) (bias dependent gate resistance which is actually channel resistance) descried in BSIM4 manual and is given by                                                      1/Rii= XRCRG1*(Ids/Vdseff+XRCRG2* Weff*ueff*Coxeff*Kb*T/q*Leff)    Please let me know.  Thanks
• Post Points: 20
• #### Mon, Jul 23 2012 1:17 AM

Re: what are rgbi and rgbd ??
 Probably - I don't really have the time to do the full research - if this is important to you, I suggest checking a later version of the documentation, or logging a service request with customer support.Regards,Andrew.
• Post Points: 5