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I am trying to build the following circuit that works as a solar power charging controller.

Unfortunately, I couldn't find IC1 named as TLC2272CP that works as dual low-noise rail-to- rail operational amplifier exhibits rail-to-rail output IC.

enter image description here

Can anyone help me rebuild this circuit design in order to replace it or is their a cheap replacement for it?

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    \$\begingroup\$ The TLC2272 is an improved version of the TLC272. You may find the latter easier. For the given application, almost any rail-to-rail/single-supply dual-OP-amp will work. \$\endgroup\$
    – Janka
    Jan 23, 2018 at 22:51
  • \$\begingroup\$ Great thanks Mr Janka kindly can you suggest to me a popular cheap one \$\endgroup\$
    – Ahmad
    Jan 23, 2018 at 22:54
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    \$\begingroup\$ The TLC272, it's €1,50 per piece. If you can't get your hands on it (unlikely), search for rail-to-rail or single-supply. \$\endgroup\$
    – Janka
    Jan 23, 2018 at 22:55
  • \$\begingroup\$ It's not available. I need it to be as cheap as you can \$\endgroup\$
    – Ahmad
    Jan 23, 2018 at 22:57
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    \$\begingroup\$ TZ1 isn't a fuse but an overvoltage protector. You want this because lightning may hit near your solar panels, creating transients on its terminals. \$\endgroup\$
    – Janka
    Jan 23, 2018 at 23:06

1 Answer 1

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IC1a is called a "float voltage comparator" in the schematic. IC1b is configured as an oscillator. The device operates from a +5V single supply.

Both sections of the device are operating as comparators, not op amps. Both functions can be achieved (better) with push-pull comparators rather than op amps because, well, comparators are designed to be comparators and low noise op amps are designed to be low noise op amps. Low noise is not required at all for these circuits to function as designed.

You can look for devices on manufacturer websites (TI, LT, Microchip, etc.) or distributor websites (Mouser, Digikey, etc.). Distributor sites are sufficient for most things, but you should look at specific manufacturer sites if you have a very specific application or requirement. Here is a Mouser page filtered to show >5V dual push-pull comparators in DIP-8 and SO-8 packages sorted by price to get you started.

My default comparator in this application would be an MCP6542, which happens to be the cheapest one on that Mouser page. (Note that it has a rail-to-rail input, but does not have a rail-to-rail output. That doesn't matter at all in the circuit.)

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  • \$\begingroup\$ If i use a pair of LM741 it will work fine !? \$\endgroup\$
    – Ahmad
    Jan 24, 2018 at 7:56
  • \$\begingroup\$ @Ahmad - Define 'fine.' The application is fairly simple and non-critical, so using op amps is feasible. Whether or not their performance is adequate depends on your requirements. \$\endgroup\$
    – vofa
    Jan 24, 2018 at 16:48
  • \$\begingroup\$ I mean that LM741 is available and its cheep while on the other hand it isn't rail to rail input or output so what you suugest !? \$\endgroup\$
    – Ahmad
    Jan 24, 2018 at 16:51
  • \$\begingroup\$ I asked for MCP6542 and unfortunately i didn't find it \$\endgroup\$
    – Ahmad
    Jan 24, 2018 at 16:52
  • \$\begingroup\$ @Ahmad - The circuit design does not require rail-to-rail input or output. Try the LM741 if it's all you've got. Oscillator frequency might change a bit (doesn't matter) and float voltage set-point accuracy will decrease (probably not much). \$\endgroup\$
    – vofa
    Jan 24, 2018 at 16:54

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