Ca3140

Thread Starter

Msinks

Joined Mar 3, 2012
22
I need a replacement for CA3140. I came across TL082CP. Can it work as a sub?
 

bertus

Joined Apr 5, 2008
19,952
Hello,

It depends on the needs.
The CA3140 has offset inputs and a strobe pin.



The TL082 is a dual opamp with none of those pins.



The TL081 does have offset inputs, but no strobe input.

I have attached the datasheets for both.

Bertus
 

Attachments

Thread Starter

Msinks

Joined Mar 3, 2012
22
My circuit shows me that i only need pins 2,3,4,6 and 7 from the CA3140. from the info u gave me, am worried pin 6 does not macth with that on the TL082.
 

bertus

Joined Apr 5, 2008
19,952
Hello,

The TL081 ia almost pin compatable.
That way the PCB (if used) does not need any changes.

Bertus
 

SgtWookie

Joined Jul 17, 2007
22,201
You need to post the schematic of the circuit you want to substitute the opamp in.

The TL08x series has a common mode input that ranges from -V +3v to +V -1.5v; in other words, it won't "see" input that is within 3v of the negative supply, or within 1.5v of the positive supply. The CA3140 has a much wider common mode input range.

Many of the newer opamps are not available in DIP packages; they are SMT/SMD only. You need to say whether you are building a new circuit based on an old design, or repairing an existing circuit.

Intersil still makes the CA3140; and it is available from AvnetExpress.com, Digikey.com, Newark.com, Element14.com, and some other authorized vendors.
Example:
http://avnetexpress.avnet.com/store/em/EMController?langId=-1&storeId=500201&catalogId=500201&action=products&N=0&mfr=ITS&term=CA3140EZ

Since it's still available, it would be a good idea to use the specified part.
 

Audioguru

Joined Dec 20, 2007
11,251
The input voltage range of the CA3140 is completely different to the TL081:
1) The input of the CA3140 can go a little below its negative supply voltage.
2) The input of a TL081 has the "Opamp Phase Inversion Problem" so if its input gets within 3V from the negative supply then the output suddenly goes positive.

The minimum supply for a CA3140 is 4V. The minimum supply for a TL081 is 7V.
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,201
If you had tried to use a TL081 with that circuit, the output LEDs would never have turned off, as the output would not fall below 3v.

I don't know what was specified for LED0. If it's a typical IR LED, then the Vf would be ~1.2V, and so (12v-1.2v)/27 Ohms works out to be around 400mA. That will fry most IR LEDs.
 
Top