Our May 2024 rotating exhibit comprises three oscilloscopes that have something in common. They all use a “Fast-In Slow-Out” (FISO) architecture to digitize the incoming signal.

The 2440 Portable Oscilloscope, introduced in 1988, uses a CCD integrated circuit.
The THS720 Handheld Oscilloscope, introduced in 1994, uses an application specific integrated circuit (ASIC).

The 7912AD Transient Digitizer, introduced in 1978, uses a scan converter CRT.

These products differ in technology implementation but are similar in architecture for digitizing incoming signals. In all cases, the FISO architecture was a product enabler.

When using a traditional analog to digital conversion, the process is limited by the speed of the A/D. An advantage is your record length can be as big as you want to make it, only limited by space and cost. The top signal flow shows a traditional A/D architecture.

Using a FISO architecture, the FISO memory device is very fast for acquisition giving you a high sample rate inexpensively. The drawback is to keep the cost low, the die size of the FISO device has to be relatively small which limits the record length that can be acquired. Also, FISO systems tend to be slightly less accurate than traditional A/D systems. The bottom signal flow shows a FISO architecture.

 

For the 7912, there weren’t any A/D converters available that operated as fast.

The 7912AD uses a digitizing scan converter CRT to draw quickly on an array of silicon diodes. A second gun can then read the diodes out slowly.

More information can be found on our 7912AD Transient Waveform Digitizer page.

 

For the 2440, the CCD was a good balance of price/performance. It uses a charge coupled device (CCD) for the signal capture. It captures the signal quickly in the CCD and read out of the CCD into a slow Analog to Digital Converter to digitize the signals.

 

For the THS720, the FISO architecture was lower power and less expensive which worked well in a handheld product.

This oscilloscope uses a Fast In – Slow Out (FISO) Application Specific Integrated Circuit
(ASIC) designed by Tektronix to  capture signals fast and digitize them slowly.

This FISO approach and technology span more than 40+ years in providing leadership products at a variety of price points.