What is a good alternative for the UA741 opamp in hobby projects?

In complement to Andy's list of criteria, I'll add that most of the time, one of the usual suspects will do just fine.

For example:

  • MCP6002 is a good one. Dirt cheap (bag of 10 is 3€). It's your crummy CMOS opamp. It is slow so it won't oscillate on your breadboard, has Rail to Rail In/Out, the input common mode even extends a little bit beyond the rails. Low power too. Performance is nothing to write home about of course, but it is good enough for many uses.

Microchip makes opamps? Well, yeah. They have a whole line of CMOS opamps which do absolutely nothing spectacular besides being cheap, RRIO, low-power, low-voltage. These work on 3.3V and 5V so a good match for Arduino, Pi, etc. If you want faster, try MCP6292 (10MHz).

Good thing with these cheap crummy CMOS opamps is they work well on battery voltages, and they don't have the LM358 gotchas, like the input common mode going to GND but not VCC, or the output being "kinda able to go to 0V but only if it never has to sink any current" and the like.

Yeah, there are other $0.50 RRIO opamps which would fit the bill. Do I want to spend 2 hours selecting a 50c opamp for a hobby project when I know this one will work? Probably not...

Also, cost. For amateur, hobby stuff, you gonna spend hours laying out that board, so when performance is needed, it's not worth it to skimp on the parts! Get a $3 opamp if it saves you a headache, it's well invested...

For example, if you want to filter and buffer a DAC or a PWM from an arduino and get a 0-5V output, there's no excuse for using an opamp which needs a negative supply voltage when you got 30c RRIO opamps which will do the job with only a 5V supply!

Audio, for example: if you need cheap, NE5532. If you need high quality, OPA1642, OPA1652, LME49720 and others in the same families are very good.

what should be the default opamp I stock in my parts bin?

It's a failure on your part to think that there is a default op-amp that suits most applications. It's as simple as that. It's also a failure to limit what you think are the important parameters to those that you have stated.

There are many important parameters that may be important to a particular target application but, these parameters may be of no-consequence to a different application.

Examples are, but not limited to: -

  • Input offset voltage
  • Input offset voltage drift with temperature
  • Input bias and offset currents
  • Input common mode range
  • Input impedance (resistance and capacitance)
  • PSRR
  • CMRR
  • Phase margin
  • Input equivalent voltage and current noises
  • Ability to operate down to 1.8 volts on power supply
  • Operating current
  • Output impedance versus frequency
  • Open loop gain

Your question is asking about the uA741 yet you quote a general application that would run on 5 volts - are you aware that the minimum recommended power supply is sometimes as high +/-10 volts with some hints in some data sheets that +/- 5 volts will be OK.

The ST uA741 is quoted to run at 5 volts but this is the exception rather than the rule.