741 op amp

[prateeksikka]

hi all!
u all might be knowing 741 ic is an operational amplifier.
it is an 8 pin IC.AND WE ALSO KNOW THAT 8th pin is not used and it is neither ground. i sometimes wonder why do manufacturers include this pin,i.e there is no need to take this connection 7 pin wont be sufficient?
comments?
prateek

[audioguru]

The 8-pin package is standard, they have never had a 7-pin package.
Many opamp circuits use the negative supply as ground.

[prateeksikka]

hi audioguru!
wat do u wish to say by writing that some opamps use -ve supply as ground what does this imply?
prateek

[audioguru]

An opamp desn't need a ground pin.

[MP]

Prateek,
It used to be standard to add a compensation capacitor between pin 1 and 8 on op-amps. This goes back to the days when op-amps were in a round "tin can" package. Then after some time op-amp manufacturers realized that frequency compensation should be built in for standard applications. Most manufacturers still offer the old style as a different part number such as National's LM301. This gives you the ability to custom tailor the compensation to a particular application. Pin 1 and 8 is still used for this purpose in these op-amps.
The 8 pin package is an industry standard and thus they will always use it. The nice thing about this is that if you have an old circuit which used the external frequency compensation capacitor, you can later plug in a newer type with better internal compensation without modifying the circuit.

Did you know you can get the 741 in a 10 pin package and a 14 pin package as well? 741J for the larger package and 741W for the 10 pin surface mount package.

MP