Path: EDN Asia >> Design Centre >> IC/Board/Systems Design >> Simple way to develop Spice macro models (Part 1)
IC/Board/Systems Design Share print

Simple way to develop Spice macro models (Part 1)

25 May 2015  | Soufiane Bendaoud

Share this page with your friends

The current-controlled voltage source has two terms: a and b.

Set the "b" term to an arbitrary value of 1. The "a" term equals the "b" term divided by 1,000. This removes the DC bias voltage across the flicker-noise diode from feeding back at the EOS source as DC error.



VN1 80 98 0

RN1 80 98 16.45E-3

HN 81 98 VN1 15

RN2 81 98 1





VFN 82 98 DC 0.6551

HFN 83 98 POLY(1) VFN 1.00E-03 1.00E+00

RFN 83 98 1

Supply current
You can model supply current with a voltage-controlled current source. The current is set with a polynomial written as:

GSY 99 50 POLY(1) (99,50) a b (19)

Set the "a" term equal to:

Is-Idq-I1-("b"*Vs) (20)

where Is is the supply current, I1, is the tail current (input stage) and Vs is the supply voltage.

Idq=kp*0.5*(W/L5)*Vdc5*2*(1+ ?*Vs/2) (21)

The idea is have the input pair driven from a supply internal to the model such that it doesn't draw external current for the model. The "b" term is simply the slope of the curve Is versus Vs from the datasheet.



EREF 98 0 POLY(2) (99,0) (50,0) 0 0.5 0.5

GSY 99 50 POLY(1) (99,50) -11.2E-04 5.00E-07

EVP 97 98 (99,50) 0.5

EVN 51 98 (50,99) 0.5

The macro models created using this technique provide very accurate results and can be tested using the collection of test circuits provided in the reference section. You can tweak the formulas based on the datasheet parameters to quickly change the models to your liking and to fit your needs. In part 2, I will address a different topology with a similar approach.

Find the collection of test circuits here

About the author
Soufiane Bendaoud is Business Development Manager-Precision Analog at Texas Instruments.

 First Page Previous Page 1 • 2 • 3 • 4 • 5

Want to more of this to be delivered to you for FREE?

Subscribe to EDN Asia alerts and receive the latest design ideas and product news in your inbox.

Got to make sure you're not a robot. Please enter the code displayed on the right.

Time to activate your subscription - it's easy!

We have sent an activate request to your registerd e-email. Simply click on the link to activate your subscription.

We're doing this to protect your privacy and ensure you successfully receive your e-mail alerts.

Add New Comment
Visitor (To avoid code verification, simply login or register with us. It is fast and free!)
*Verify code:
Tech Impact

Regional Roundup
Control this smart glass with the blink of an eye
K-Glass 2 detects users' eye movements to point the cursor to recognise computer icons or objects in the Internet, and uses winks for commands. The researchers call this interface the "i-Mouse."

GlobalFoundries extends grants to Singapore students
ARM, Tencent Games team up to improve mobile gaming

News | Products | Design Features | Regional Roundup | Tech Impact