IV Converters, PA630 IC?

Some of the recent discussion on I/V converters and op amps loosened some memories. One that I remember reading about some 7 or so years ago was an IC called a current converter. The part number was PA630. As I recall, it was NOT an op amp, but a numer of current mirrors one could configure to follow a DAC, addressing a number of the performance issues mentioned with op amps in recent discussions.

I never bought or otherwise sampled any of these devices and was wondering if any of you did. If so, what did you think? And why is it there doesn't seem to be much info on this device on the web? This link to Wadia info makes me think maybe Wadia secured the rights to this device.

Just curious.
I have just followed Nelson's design for I/V conversion to an I out from a DAC.I have a little prototype drawing likely to work:


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Re: PA630

Yes; this is the device. You also found all I could find on the device and the company via the web.

I remember at least one company some time ago bragging about their IV converter using this device and its superior performance to conventional opamps with feedback. I'm still check my papers here....

Also, as I recall it was not a cheap device,built on DI process. Maybe $30 USD per chip?

I'm curious what Jocko means ... patent infringment maybe?

mlloyd1 :)

Elso Kwak said:
Hi Mlloyd1,
You mean the current-conveyor by Photonics?
Could not find a website yet.:confused:


2001-11-21 2:51 pm
G.Z. China
The idea is quite old !

Eveyone whom has learn about the current mode technology would knew the part PA630 & PA630A! It was present as a classical design of current conveyor in the textbook. And, one of it's typical use which was present in textbook is a open-loop I/V convertor for audio application!!! I guess that the DAC in the textbook is PCM-XX or AD-XXXX.

I'm very curious how can Wadia get the patent.
To get a patent is so easy like this? :p
Pjotr said:
Deja Vu :xeye:

Look here



I am making the assumption you are not replying to you own post but the one before it?

If that is the case the MAX435 is not an equivalent to the OPA660. If you have a look at the data sheets you will see they are a little different. Although they are both called transconductance amplifiers.

It has lots of applications for open loop audio applications which the OPA660 is not capable of.

I apologise if I strayed of the post a little but as I said I thought it was an interesting chip, for its other applications also since current conveyors or mirrors were being discussed.

Is that alright?

Best wishes, Craig
Hi Craig,

I was replying to your post indeed. I know the MAX435 as well as the MAX436. I have used them for modulating laser diodes at 100 MHz. In that application the OPA660 performed much more linear.

I never tried them for audio IV-conversion. It would be nice to investigate them. The MAX’s can handle more current but the OPA660 is much faster. Speed can be of benefit to handle the relative fast current pulses coming out of the DAC without slew problems or going partly into saturation. This is the main reason why “audiophile” op-amps can’t do the job IMHO.

Don’t have the idea that this off-topic, maybe Jocko can tell? He seems to know more about the PA630.

Cheers Peter