SMD Discrete Op Amp

[3nity]

Samuel are you saying that SMD parts are less short circuit proof?

If its the case a trough hole version would be more short-circuit proof?

If there;s a risk of short-circuit what would be a safer way to achieve it?


I'm trying to understand the wolrd of DOA's

 

[burdij]

The test fixture for checking the partially stuffed boards is ready:

 

[kato]

Ooooo, that is very cool.
:thumb:






(do we all have that same multimeter????
I think we do.)

 

[3nity]

Burdij, how are you testing it?

 

[burdij]

The fixture has a X100 inverting amp setup with the DOA. I will look at offset, PS current in, gain, frequency response, and distortion, I think. I expect all of these to fall into a fairly narrow range since some of these will depend on the input transistors which are one of the parts off the board (implemented by the fixture).

 

[Samuel Groner]

Samuel are you saying that SMD parts are less short circuit proof?

When driving a short the heat dissipation of most parts is at its maximum. As SMD parts are smaller (i.e. lower thermal mass and smaller surface) they are prone to have lower dissipation limits. However, as the analysis has shown, we are still within the limits for this specific device so they should not fail.

Samuel

 

[rlaury]

Hi Group
It will be interesting to see how the noise figure works out.
Also the matching of the transistors and the R's is very difficult with SMD.
Have we started ignoring these requirements?

Just curious.

RonL

 

[burdij]

The input pair consisting of two 2N5088 in TO92 is being matched for beta and Vbe. I am not matching the second differential pair as these are SMD parts. The 2N5088s are billed as low noise parts, according to the data sheet, <3db in the collector current range used in this application.

 

[Baltimore]

any news on these?

 

[burdij]

I am providing some of these to 3nity for his 312 preamp boards. I will have additional units stuffed and tested before Monday of next week. I also need to write up some basic assembly instructions. I will post in the Black Market when these are ready. These will be semikits including the thru hole parts and pins. Here are some views:

 

[Baltimore]

awesome! any idea of price?

 

[3nity]

Completely awesome!!

 

[Nadege]

really cool,

which schematics did you use for the 2520 SMD ?

 

[Tubemooley]

Those look killer. I'm in for at least 4 pieces when they show up on the Black Market. DW.

 

[vertiges]

[quote author="Nadege"]really cool,

which schematics did you use for the 2520 SMD ?[/quote]

Nadege, the answer in on the page one of this thread ! :wink:

eD)))

 

[burdij]

For those people who expressed an interest in getting the semi-kits of this op amp, I have a small number available.

Here is a link to the Black Market:

http://www.groupdiy.com/index.php?topic=318828#318828

 

[burdij]

I have been getting together the parts for the rest of the preamp module. This picture shows the project so far:

I have one more board to be sent for manufacturing. It is the 8 segment level indicator shown on the far right. This level indicator will show full-wave peaks at -30db (essentially a signal presence indication) and then -18db to +18db (a little shy of clipping at +20db) in 6db steps.

This version has Cinemag iron, the traditional CM75101APC and the CMOQ-2S.

 

[Samuel Groner]

Like the look--very tidy, neat and pro! :thumb:

Samuel