I've just been stripping down old circuit boards and now have a spare LM723CT voltage regulator IC.
Are these now "old hat" and have been replaced with better devices ?
Or is it worth keeping and using in a PSU in the future ?
Are these now "old hat" and have been replaced with better devices ?
Or is it worth keeping and using in a PSU in the future ?
I have some as well.
You can make very useful linear regulators with LM723. You can make similar linear voltage regulators with other ICs as alternative. LM723 offers good flexibility and is good for design-training. What is the most rational choice? - the IC you already have in your drawer and can do the job.
You can make very useful linear regulators with LM723. You can make similar linear voltage regulators with other ICs as alternative. LM723 offers good flexibility and is good for design-training. What is the most rational choice? - the IC you already have in your drawer and can do the job.
That chip contains two opamps with one used as a voltage reference buffer and the other as an error amplifier which drives the output through a transistor. You can use that chip, but it is a linear regulator which are notorious for energy inefficiency. With a 78** or 79** chip you can achieve the same thing with less hair pulling. These chips provide a fixed regulated output, but that limitation can easily be overidden by using a voltage divider at the 'common/ground' pin.
It can be configured as a switch-mode regulator too, according to the datasheet, its kind of a toolkit for making regulators.
These are very low noise regulators BUT they are not LDO. need a minimum voltage to function OK too and they need a pass transistor for some serious current.
They are not to be compared to 78xx as these are way lower in noise numbers.
They are not to be compared to 78xx as these are way lower in noise numbers.
The reference on board is a true buried zener, c.6.9v - so very quiet - and the output has a convenient pin for adding a cap to decouple this. I've used half of 723s just as nice quiet voltage references before - you only need to apply power to the reference supply pin,, a 10uF cap and iirc the specification for that reference output is single-figure uV. It's still a useful part.
2.5 µV output noise voltage when a 4.7 µF cap is used. Way better than many modern regulators. The PSU we designed for the Subbu DAC used one and many were laughing ... until they noticed the performance.
I wouldn't use it for above let's say 15 W applications anymore though as it needs a higher dropout voltage resulting in generated heat. Some don't mind but I like cool and green design when possible. However, being able to use it for higher out power is one of the features of LM723 🙂 Some modern regs outperform LM723 and have the benefit being LDO. Lower part count too so smaller, less heat etc.
I wouldn't use it for above let's say 15 W applications anymore though as it needs a higher dropout voltage resulting in generated heat. Some don't mind but I like cool and green design when possible. However, being able to use it for higher out power is one of the features of LM723 🙂 Some modern regs outperform LM723 and have the benefit being LDO. Lower part count too so smaller, less heat etc.
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