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I can't find the OPA132/134 family of op-amps in my country (Hong Kong)

post #1 of 8
Thread Starter 

I am looking at the store in HK. I can't find the OPA132/134 family of op-amps here, but a list of other op-amps.

Can anyone help me to find a suitable op-amp for a cmoy out of this list?

Or what kind of op-amp should I choose for it?

Please help.....

http://www.weclonline.com/tchi/productlist.asp?page=1&mc_code=08&sc_code=006&s2c_code=0003&s3c_code=0003&display=photo

post #2 of 8

Assuming you want dual opamps I can see

 

TL072

TL082

NS353 - looks to be the same as the LF353 which I use lots of :-)

TI 5532

 

cheers

FRED

post #3 of 8

You can prob order from RS-Online HK, free delivery :)

post #4 of 8
Thread Starter 

i have one more question..

if i am using a 9V battery for my cmoy. I want a switch which has an indicator light with it, what voltage of the switch should i choose?

I have a 220-250V with me now, i guess it doesn't work right?

and what does pin 1,2,3 means on  the switch?

post #5 of 8

Lighted switches with a voltage rating effectively contain RLED and D1 from my schematic. The only reason they have a voltage rating is that they have picked the appropriate RLED rating to give suitable light output in the LED, D1. Such switches usually have common DC power supply voltage ratings of either 5V or 12V.

 

The data sheet for the switch should give some indication that this is what they have done. Ideally, you should see the LED and resistor in the switch schematic. If not, at least they should indicate the resistance.

 

Depending on how they have chosen the RLED value, you might be able to get away with a voltage difference as much as 2x, but you can't count on that. So, you might burn out a "5V" switch with a 9V powered CMoy, but you could probably get away with a 12V switch, no problem.

 

It is far better to get a switch with the LED in it only, without the resistor. Then you can calculate the RLED value as shown in my guide.

 

As for your "220-250V" number, I would guess that this doesn't talk about the LED path through the switch at all. That's going to be the voltage rating on the contacts in the actual switch. Such switches are sized for AC wall voltage applications. You can use them for low-voltage DC applications like a battery-powered CMoy pocket amplifier. Such switches are simply physically larger than actually required, in order to withstand the higher voltage.

 

As for the "pin 1-3" issue, it depends on the switch. There is no standard numbering system. You'll have to show us the data sheet if you want us to comment on specifics. I would guess that a lighted switch with only three connections wouldn't be suitable for this application, however. You'd want one with four connections, since you need the LED path to be separate from the switch path in a CMoy pocket amplifier.


Edited by tangent - 2/24/13 at 5:31pm
post #6 of 8

Since posting the above, I've thought of a fix for the problem where your chosen lighted LED is set up for 5 V and you have to run it on 9 V. You simply have to infer the resistor they used and add an additional external resistor in series with the LED path.

 

The trick is performing that inference.

 

If the data sheet gives the resistance, you simply use the equations from my guide, then subtract the provided resistance from the calculated resistance to give the value you need to add in series.

 

The data sheet might instead give the current through the LED path only, in which case you can make a pretty good guess. If it's a red LED, you can guess that it has a Vf of 1.8 V, so the drop across the switch's internal LED current-limiting resistor must be approximately 3.2 V with a 5 V power supply. If the data sheet quotes, say, 5 mA, you can guess that the resistor must be around 640 ohms. If you want to maintain 5 mA through the LED for the same brightness at a 9 V supply, my equation tells you to use a 1.4 K resistor, so you subtract 640 ohms from that and get 800 ohms. Then of course you'd round that up to a value you can actually get, such as 820, 910, or 1000 ohms.

 

Of course, you don't have to keep the same brightness level. You could just whack a 2K - 10K resistor in there instead, knowing it will end up a bit dimmer than stock while saving some power.

post #7 of 8

Hello Logosway. The choice of audio op amps you chose are far superior to any in the store you are looking at OPA132/134 the others mentioned are backward technology. The OPA 132/134  series has now been bettered by the LME 49710 series did=    distortion= 0.ooooo3%At ikh I have used all the others mentioned in the past  s  25YRS and they are out of date. The problem is the electronics world has moved on to SMD miniature components and no longer supports the DIY lobby as there is not the financial rewards.You will have to try specialist active device companies.if in China then an industrial company . otherwise it would need to br  be Japan/ Australia/ UK/ USA.If you want to post again maybe I can find a supplier for you . In the UK there are suppliers with the ones you want.Good Luck and a good Water Snake Year.
 

post #8 of 8

Also a mention for other stores:

Mouser has free shipping to hongkong for 750HKD

element14 (Farnell) has free shipping for 200HKD

 

online ordering has far better choices than WECL or ap liu street in general. You cant get audiophile stuff from these online stores but those are once in a while things.

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