I need a replacement for CA3140. I came across TL082CP. Can it work as a sub?

 

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

 

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.

 

Hello,

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

Bertus

 

thanks bertus, u rock

 

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...201&action=products&N=0&mfr=ITS&term=CA3140EZ

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

 

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.

 

am trying to make a remote control extender so i can control an appliance from another room. this is the link for the image of the circuit; http://makecircuits.com/downloads/circuits-and-diagrams/infrared-based-schematics/irext.gif

 

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.

 

thanks for help guys