Re: Great Movie Line from an Old Bob Hope Movie

I'm having problems with Multisim 7 and opamps. I try to simulate simple comparator which uses TL074 opamp, but the output voltage is something like 2.6 teravolts!? I have tried with other opamps, but the results are similar. Can anyone tell me why this happens? Thanks

LT Spice from

Anyone have a 1496 (Gilbert Cell Multiplier) Spice Model ??

I could roll my own but I'm unsure if the I/C models I have, of that vintage, would be correct.

Thanks!

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

The models might be correct, but would they do you any good? When I started designing ICs, bipolar devices could be designed one by one, and you started a few years before I did. The design manual for the first process I worked in was four pages long, and lists geometry-based equations for those parameters that weren't considered constant. For example:

Rb = (Rcb/Wbc + (2Rb*Lbe/We))/n + K*Rbp*Le/We

Rcb = 19sqrt(Rb) Rb = base sheet resistance Rbp = pinched base sheet resistance n = 1 for single base stripe, 2 for double base stripe K = 1/(12*(1+(Le/We)^2))

Wbc, Lbe, We, and Le are transistor dimensions.

In all, I have 10 dimension parameters shown for a simple single-base stripe transistor - for complex geometries we were expected to make our own models. Every transistor had its own model.

So, the question is, even if you knew your models were good, how would you know which models to use?

-- Mike --

Hi Jim,

This may be a bit too brief of a model but just in case it suffices for your application:

I don't know anything about the accuracy or the source though. Thought you don't use Gilbert cells ...... :-)

Regards, Joerg

Designing your own transistors disappeared from the scene LONG ago.

There are 61 bipolar model parameters... now-a-days supplied by the foundry for each device size/shape.

Rolling your own custom device size/shape is generally no longer allowed.

I have some Semtech models for a process dating from the vintage of the 1496, and would probably suffice, but I was hoping for a subcircuit specifically done for the circuit.

...Jim Thompson

Why don't you just "wire up" the individual fab transistors you'll actually be using?

Thanks, - Win

(email: use hill_at_rowland-dot-org for now)

It's not for one of my custom jobs... I'm just trying to be a good samaritan and doing an off-the-shelf-component design for a lurker here.

Now-a-days I deal with bipolars with fTs that were only a wet dream when the 1496 was designed ;-)

My device library presently includes models for 53 different processes... all but one no older than 4 years... the Semtech models are from a late 60s, early 70s, process that's still being used for "HV" (12V) bipolar chips.

...Jim Thompson

I have Multisim 2001 Power Pro edition. For some reason I am having dificulty simulating the 555 timer on long delays. By long I mean in the area of 20 seconds. I am designing an astable multivibrator with a

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Why not dump it for a free program that works better, anyway? LT Spice (from

I asked a question before and received answers which, although helpful to some extent, did not provide me with what I need to know. So, I decided to rephrase the question.

HI' I am yar intellegence then I decide send my problem to solve it for me .I want to make a timer circuit to control 4point with this following specification :

2- point two connect for an adjustable time with(variable resistance)then point two disconect and point three is connect

4- point four connect for an adjustable time with(variable resistance)then point four disconect and point one is connect another time

note: my problem is how can make the first circuit (555) triger the next circuit IF there is aanother useful IC's to catch my goal then why not

note :I try this circuit but it isnot worked right

pin1----gnd pin2----10k resistance&in4148diode&connect to the next 555 pin 3 pin3----connect to a coil relay pin4----connect to pin8 pin5----connect to 0.01 uf ceramic capacitor(the capacitor in between pin 5 &gnd) pin6----connect to 1000 uf&25volt electrolytic(polar)(the negative leg is connected to gnd)&39k ohm connected in between pin6 & pin7 pin7----connect to 1 M ohm variable resistance in between pin 7&pin 8 pin 8----connect to the vcc (the power supply is 12volt adapter)

I want any help

thank you YAR

Didn't it get soggy there in humidity land ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

I was using 1496's before I even began designing ICs, and I designed many of my own transistors until around 1990 - many years after the advent of the 1496. There are only a few transistors in the 1496 - wouldn't the designers have been more likely to design their own?

-- Mike --

If by "design" you mean choose the layout, yes, but there were no models in those days, only breadboards. I've stretched many a base region to allow a crossover when all we had was single-layer metal. The "matching" devices were stretched also, even if they needed no crossover.

...Jim Thompson

..model Q2N5179 NPN(Is=69.28E-18 Xti=3 Eg=1.11 Vaf=100 Bf=282.1 Ne=1.177 Ise=69.28E-18 Ikf=22.03m Xtb=1.5 Br=1.176 Nc=2 Isc=0 Ikr=0 Rc=4 Cjc=893.1f Mjc=.3017 Vjc=.75 Fc=.5 Cje=939.8f Mje=.3453 Vje=.75 Tr=1.588n Tf=141.1p Itf=.27 Vtf=10 Xtf=30 Rb=10)

Add "+" appropriately at each newline.

...Jim Thompson

Does anybody have a source or could post s spice model for a 2N5179 V/UHF transistor?

-- Leland C. Scott KC8LDO

Wireless Network Mobile computing on the go brought to you by Micro$oft

Jim et al:

I used to keep all the IC models I needed on one of my wife's 4x5 inch recipe cards tucked into my shirt pocket.

But.. those days are now gone forever...

-- Peter >

started

those

own

you

Couple months back I purchased Circuit Creator Pro PCB Design Software for just $195. By now, have designed 7 PCBs and got the boards made. Software has worked very well. It has some features available in expensive package like Orcad. Demo can be downloaded from following link.

Thanks, Mark