I’m behind schedule, so this week we will have 3 chips (from the same family). Instead of reviewing some fancy shmancy ASIC, we’re going to get back to basics with a nice, cheap opamp set.
Cause sometimes you just want an opamp. Nothin’ crazy, just want to add some voltages, maybe amplify something a bit. Possibly do some filtering, or interface to a sensor, or some audio stuff.
Well, my friend, the TL08x’s are your bread & butter.
4 MHz gain bandwidth (internally compensated)
Not rail-to-rail so 8V rail is minimal, a split +-15 is great but even +- 5 is good to go
Input offset voltage is <15mV
Input bias current <8nA
JFET input stage so you’ve got a ridiculous 10^12 (1 Mega-Mega ohm!) input resistance
<2.8mA/opamp quiescent current
13V/us slew rate
noise figure: 25nVrtHz
Lets compare it to the ye olde favorite, the LM741:
1 MHz bandwidth
Input offset voltage: <5mV
Input bias current: <800nA
Transistor input stage, >300Kohm input resistance
<2.8 mA quiescent
0.5V/us slew rate
noise figure: 30 nVrtHz
So the worst case offset voltage is better on the ‘741, but the gainbandwidth, the input resistance, input bias current and the slew rate sucks in comparison to the ‘081. And the 081 is a little less noisy too.
The dual in 8DIP is a mere $0.64 from digikey, mouser has them from STMicro for $0.37. Thats cheaper than a cup of coffee!
So, when you want to have a stash of opamps for prototyping, these are your best bet. I especially like just having the duals and quads around, and then swapping out a better specified opamp later on in the project if it’s called for.
The offset voltage usually isn’t so horrid, of course, although I still suggets coupling AC if you’re cascading gain stages. Congratulations, TL082, you are the Chip of the Week!
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