opa 541 question

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millwood

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Joined 2003
I am trying to build one. it shouldn't be more complicated, especially if you forgo the current-sensing resistor. the datasheet I believe has both inverting and non-inverting designs.

I am adopting the inverting design, using the same resistors / caps from my lm3875 gainclone.
 
JOE DIRT®

JOE DIRT®

Member
Joined 2003
I managed to build a test circuit for the OPA 541 and used parts I had at hand.
At the input I have a 100k clarostat pot feeding a MKP 1.5uf poly cap. From there on I have a 10k metal film on the inverting input with a 220k metal film for the feedback network.
For the power supply I chose to use the 2 Elna 15 000uf caps bypassed with some Philips 0.1uf poly caps....I`m getting a solid 26vdc out from this setup.
So far I have just injected a 1000hz sine wave at 2v into the input and things sound ok. I chose to use the current clamping resistor as I had a nice 0.1ohm 1% 15 watt metal film resistor handy and wanted to be safe.
I havent made any crucial measurements yet as I let it run over night........I`ll post my results when I do.........I`m going to interested in comparing the 3886 I have yet to build.


Cheers!!The DIRT®
 
Mad_K

Mad_K

Member
Joined 2002
What rails are you using?

If you look at the following chart, I'm not shure how safe you are....:bawling:
 

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Mad_K

Mad_K

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Joined 2002
Here we see what Rcl to use after having studied the SOA:

Seems I also read the datasheet a little too fast before, as I adviced someone to use 0R1/0R15 with the opa541 am/ap respectively. Consulting the SOA chart and the graph below we see that with 35V rails we have to use 0R4 to be safe (1,8A limit)...:dead:


edit:

(Note that I'm not using any resistor at all in mine, nor does MatttCattt either I believe) -We're "fearless DIY'ers". ;)

This makes you think about the other chips, with pre-programmed protection (eg LM3875), and how safe they really are. I've read several places about people having fried their chips with shorted outputs/other nasty habbits. After all, why should we bother with CL in a chip, whilst we don't with the other (discrete) amplifiers we build? I say; leave it out, enjoy the fat sound, and don't do nasty things to your amps! ;)
 

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e.lectronick

e.lectronick

Member
Joined 2002
Do they need to be matched?

Hi, guys.
I have a Noob question: I've just purchased a couple pairs of OPA541 and I'm wondering if they need to be matched as pairs the same way individual FETs do?

I kind of figured that the variances in performance of an OpAmp from one chip to another would be minimized by design, but I really don't know.

Thanks
-Erik.
 
G

GregGC

Member
Joined 2003
Re: Do they need to be matched?

e.lectronick said:
Hi, guys.
I have a Noob question: I've just purchased a couple pairs of OPA541 and I'm wondering if they need to be matched as pairs the same way individual FETs do?

I kind of figured that the variances in performance of an OpAmp from one chip to another would be minimized by design, but I really don't know.

Thanks
-Erik.
Click to expand...

Dont need to much them if your design isn't too much "cutting edge".
 
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