Using TL084 or TL074?

[gbowne1]

Hi all!  What would help me figure out which TL074 or TL084 to use?

Looking at the data there is a lot to choose from to narrow it down.  But I got a little lost in the datasheets.  I've used other TL0** type IC's but this pair is a little confusing.

They are opamp IC's of course.. so they have a +4v/-4v input rail and seem to be a 70 to 80db Common Mode Rejection Ration (CMRR).

Voltage and Bias current @ 15v w/ different values.

The application needs a 14pin package.

They both come from STMicro or TI.


Greg

[allanw]

Dunno if you saw this, but TI's site says "TL081 - Similar parts, where TL08x is a general purpose family and TL07x is a low noise family"

[gbowne1]

No. I didn't see that.  Low noise would be nice.  It's an RF Application.

[tecman]

No. I didn't see that.  Low noise would be nice.  It's an RF Application.

RF should mostly not be related to the op-amp.  The low noise refers to internally generated noise in the op-amp.  The op-amp noise will be much lower in spectrum than RF.

If you are working in mV signals, lo noise can be a benefit.

Paul

[Zad]

The gain-bandwidth product on the TL08x is only 4MHz anyway. That is to say at 4MHz, max gain is 1, 2MHz it is 2, 1MHz it is 4 etc. There are RF op-amps, but that isn't one.

[gbowne1]

Project: RF Power Amplfier for 87MHZ - 108MHz FM

Output Min.: 500w ERP
Output Max : 700w ERP

RF Input @ drive: 7w

Thinking about using a BLF278 by NXP Semiconductors they are about $150.

Or maybe one of the MRF transistors.

GReg