Zener regulator with "integrated" pre-regulator

[00940]

According to TI's datasheet for ne5532:

- max recommended operating voltage +/-20V (absolute stress rating +/-22V).

- 32V output voltage swing into 600R with +/-18V supply.

I can thus use the NE5532 up to 2V of the rails. Using a red led (with a 1.8V dropout) gives me a PS rail of 19.7V. The NE5534 must output 17.2. Difference ? 2.5V which should be ok.


If I use the "sinking current" strategy of the super regulator + the bootstrapped supply, I must not only add the parts needed for a CCS but also another opamp (I can't use dual since they need to be grounded). It will seriously raise the cost and space needed. I'm aware the suggested reg won't be as good as the Jung's, by far. If it's better than the LM317, that's ok for me.

[AndrewT]

Originally posted by 00940
According to TI's datasheet for ne5532:

- max recommended operating voltage +/-20V (absolute stress rating +/-22V).

that's a total absolute maximum supply voltage of 44vdc.
You can run them at 42Vdc if you guarantee that they never exceed 44Vdc during any operating condition.

[00940]

Originally posted by AndrewT
that's a total absolute maximum supply voltage of 44vdc.
You can run them at 42Vdc if you guarantee that they never exceed 44Vdc during any operating condition.

Do you mean that I should make use of that extra volt to increase the supply of the ne5534, in order to increase the difference in between rail and output to 3.5V ?


btw, R4 should be scrapped, it's a leftover of the flea regulator which was the basis of this design. It makes no sense with a medium power pass transistor. One should also probably increase C6 to a 100uF, not low-esr, cap (or low-esr + 0.5r in serie).

[AndrewT]

How many times do we need to repeat it.
It's not an extra volt of supply capability.
You have 23V of extra supply capability.

[00940]

compared to Jung's yes, I know it (I read all his articles a long time ago).


This reg is less than half the price in parts than a Jung's.

[00940]

*sighs*

sorry, too tired to think straight. What i meant is that using + - 20V allows me to use one ne5532 for a positive and a negative supply, saving space and cost.

If you think that 2.5V between output and rail isn't enough, I can lower the zener value and use a led with a higher dropout.

[AndrewT]

But, you don't need a dual polarity supply.
Both the inputs and the output are well above ground voltage.
The negative supply pin can be connected to ground, thus halving the voltage across the supply pins.

[00940]

I'm affraid I have not been crystal clear... The circuit powered by this regulator needs a dual supply. I'm not building a negative supply just for the opamp. One half of the ne5532 will take care of the positive supply and the other half of the negative supply (with an extra lm337, bd140 and so on).