I see no benefits at all !!!
The schematic might work - if you've successfully simulated it.
The output voltage might be well regulated, concerning ripple rejection from the mains, but the output voltage itself is not 'really' regulated. In fact it will vary with temperature, etc. based on the fact that Q1/Q2 acts as a Darlington emitter-follower and that there's no feedback from the output.
What should this circuit basically do for you???
I don't really 'see' an application where this circuit is desired - so please explain what you had in mind and why you've designed it. What should be the goal for that circuit?
The schematic might work - if you've successfully simulated it.
The output voltage might be well regulated, concerning ripple rejection from the mains, but the output voltage itself is not 'really' regulated. In fact it will vary with temperature, etc. based on the fact that Q1/Q2 acts as a Darlington emitter-follower and that there's no feedback from the output.
What should this circuit basically do for you???
I don't really 'see' an application where this circuit is desired - so please explain what you had in mind and why you've designed it. What should be the goal for that circuit?
Corax said:
Well, I know what a darlington is and I know the circuit will drift a bit. It is also quite clear it has no feedback.
Aim of the circuit ? Feed a discrete I/V stage.
What I had in mind ? Try first something else than the usual lm317, with better high frequency rejection. Secondly, try to improve the local regulators used by rbroer on his I/V : http://www.diyaudio.com/forums/attachment.php?s=&postid=262355&stamp=1068412889
Well, for this intended purpose I guess the circuit is OK.
No feedback won't make any trouble with oscillation tendencies, basically.
The only weak point is still the use of the LM317 which is a little bit noisy in my opinion. Use a low-noise reference element and a more traditional regulator design with transistors and I'll vote for your design.
On the other side your design would be fine if I would consider the parts count and PCB space necessary for a traditional design. So, under some aspects your design is flawless and it'll do what it's supposed to do.
No feedback won't make any trouble with oscillation tendencies, basically.
The only weak point is still the use of the LM317 which is a little bit noisy in my opinion. Use a low-noise reference element and a more traditional regulator design with transistors and I'll vote for your design.
On the other side your design would be fine if I would consider the parts count and PCB space necessary for a traditional design. So, under some aspects your design is flawless and it'll do what it's supposed to do.
If you use an opamp that can work with the supply you have (+15? +5?) there's no need for a negative supply. Just ground the -supply pin.
Actually, you seem to be on the road to reinvent the 'super-regulator' with pre-regulator 😉
Jan Didden
Actually, you seem to be on the road to reinvent the 'super-regulator' with pre-regulator 😉
Jan Didden
@00940:
I didn't feel that your tone was a bit harsh.
Since I couldn't find any information about your education(s), skills, etc. I can only guess about someones knowledge and that you're a PSCI(?) student doesn't make any sense to me because I don't know what this abbreviation stands for. Sometimes I've just a feeling that he/she knows a lot sometimes not. The latter case I assumed in your case I must admit. So I guess I have to apologize.
Nevertheless your last design is much better and I agree with Jan to omit the negative supply for the OpAmp.
I didn't feel that your tone was a bit harsh.
Since I couldn't find any information about your education(s), skills, etc. I can only guess about someones knowledge and that you're a PSCI(?) student doesn't make any sense to me because I don't know what this abbreviation stands for. Sometimes I've just a feeling that he/she knows a lot sometimes not. The latter case I assumed in your case I must admit. So I guess I have to apologize.
Nevertheless your last design is much better and I agree with Jan to omit the negative supply for the OpAmp.
janneman said:
Well, maybe but I don't think I'm willing to go further down the road 😉 There are still some major differences, though (better opamp, way to provide current to the voltage reference, better voltage reference, a few caps and resistors, gain for the voltage reference, etc.).
The PS should give around +/-16.7VDC as is (easily changed by changing the zener value). Bad news is the heavy dropout at around 6.5VDC minimum.
Wrt the negative voltage: I'll be building both positive and negative supplies, so I'll have one available. The whole thing will be more compact with a ne5532 with +/- supplies. The operating voltage is close to the limit though... about +/-20VDC.
@Corax: I should update my profile, it's a few years old now. PSCI stood for political science (it was rather stupid to put that into the profile I admit) but I'm now working for the Jesuit Refugees Service. Nothing related to electronics as you can see 😉
@Corax: I should update my profile, it's a few years old now. PSCI stood for political science (it was rather stupid to put that into the profile I admit) but I'm now working for the Jesuit Refugees Service. Nothing related to electronics as you can see 😉
the 5534 & 5532 can take about 42V across the supply pins.
20V is well within this limit.
But you are asking the opamp to operate with the input pin voltage very close to the positive supply rail. They are not rail to rail opamps.
Take the hint from Janneman and go and read up on super regulators at Walt Jung's site.
20V is well within this limit.
But you are asking the opamp to operate with the input pin voltage very close to the positive supply rail. They are not rail to rail opamps.
Take the hint from Janneman and go and read up on super regulators at Walt Jung's site.
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.
- 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.
that's a total absolute maximum supply voltage of 44vdc.00940 said:
You can run them at 42Vdc if you guarantee that they never exceed 44Vdc during any operating condition.
AndrewT said:
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).
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.
It's not an extra volt of supply capability.
You have 23V of extra supply capability.
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.
This reg is less than half the price in parts than a Jung's.
*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.
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.
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.
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.
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).
- Status
- Not open for further replies.