Wadia Swift Current?

[Cameron]

Does anyone know anything about the Wadia Swift Current I/V converter? I will try to look up any patent information. The following is a quoted directly from their site:

Conventional digital-to-analog converters perform current-to-voltage (I/V) conversion using feedback circuits based on operational amplifiers. Because the signal from the DAC chip consists of a series of step changes, the distortion introduced by this feedback circuit is a significant limitation on sonic performance. In contrast, the Swift Current circuit performs this I/V conversion with Wadia’s patented current-conveyor integrated circuit (IC) that eliminates feedback. This bipolar IC consists of an innovative connection of Wilson current mirrors, an emitter degeneration compensation scheme to optimize transient response and stability, and a novel current mirror arrangement to enhance output impedance.

[Cameron]

Nevermind. I found a previous thread which answered my question. Apparently there is no information available about the circuit they use or the PA630 IC. Could not find the patent either.

[jam]

Cameron,

I believe the PA630 is a current conveyor. The internal circuit might have been published in Wireless World years ago.

[Forrest Carter]

US patent number 4983930

[janneman]

Originally posted by jam
Cameron,

I believe the PA630 is a current conveyor. The internal circuit might have been published in Wireless World years ago.

Correct. The PA630 (and the '630A, which has connections for dditional FET drain followers at the output) was taken off the market a couple of years ago after the designer sold the rights and his remaining chips to Wadia. There have been at least two publications in EW/WW, plus several in the trade press. There is also a full chapter describing these chips in the book "Analog IC design, the current mode approach".
If you need info like internal schematics etc, drop me an email.

Jan Didden