Hints & Tips

Q. How can I use the S3245 Noise amplifier with or without UTMOST?

A: The S3245 Noise amplifier is a stand alone low noise amplifier which includes the DC bias filterings. The S3245 has four DC inputs connected to the DC parameter analyzer and four DC outputs connected to the DUT. The input connectors are triax and the output connectors are BNC type. The amplifier also has one more BNC connector to interface to the Dynamic Signal Analyzer for Flicker Noise measurements. The DC signals which are coming from the DC analyzer are filtered inside the Noise amplifier box. The DC bias for the op-amps are supplied by the shielded DC power supply which is also part of the S3245 Noise amplifier box.

The S3245 Noise amplifier is used for Flicker Noise measurements on MOS devices. The S3245 amplifier does not have any GPIB interface and can be operated without UTMOST's control. In manual operation the DC biases should be supplied manually. The user should also set the Dynamic Signal Analyzer to measure the Power Spectrum Density of the Noise Voltage and compensation of the amplifier gain including the system noise. The Noise Voltage to Noise Current conversions and Noise parameter extractions should be cariied out manually.

The Noise module in UTMOST's MOS technology is modified to automate the Noise measurement using the S3245 Noise amplifier box, Dynamic Signal Analyzer and DC parameter analyzer. UTMOST Noise routine will allow users to specify multiple DC bias conditions. The DC analyzer will be controlled by UTMOST to supply the defined DC bias conditions (Figure 1.) to the S3245 input. The necessary settling delays are introduced by UTMOST for DC line filters to function properly. After the the device noise is amplified the Dynamic signal analyzer which is also controlled by UTMOST ( UTMOST currently supports the following Dynamic signal Analyzers HP3561, HP3562, HP35660, HP35665, HP35670 (Figure 2.)) will start the measurement of Power Spectrum Density of the Noise Voltage. The measured noise will be displayed on UTMOST graphics screen and the same measurement process will be repeated for the other specified DC bias conditions. The user can also utilize the "fit" option from the graphics screen to extract the Noise paramaters (including BSIM3 Noise parameters). The extracted SPICE parameters can be verified by using UTMOST's SPICE simulator interface and measured and simulated noise curves can be overlayed. The user can also exercise the "Global Optimization" option to improve the noise parameters.



Figure 1. Noise Measurement Routine Setup Screen.


Figure 2. Hardware configuration screen with new DSA instrument drivers.


The measured Noise curves can be stored in UTMOST log file format and measured versus simulated noise curves can be plotted. When multiple DC biases are used the VDS and VGS voltage versus KF curves can be obtained.



Q: What SOI models are supported by SmartSpice and UTMOST?

A: SmartSpice currently supports five SOI models:

  • University of Florida, non-fully and fully depleted models,
  • University of Southampton, STAG SOI model,
  • Berkeley BSIM3 SOI model,
  • Honeywell SOI model.

SOI devices are instantiated in the input deck as MOS devices and the respective level numbers for the models in SmartSpice are Level 21, 22, 24, 23 and 20.

Shown below is an example of a device using the STAG model. This particular device has 6 terminals.

M1 d fg s bg sub th nmod l=1u w=1u
.MODEL nmod NMOS (
+ Level = 24
+ ......
+ )