The simplistic Salas low voltage shunt regulator

[merlin el mago]

With current over 200mA don't need the Rs cap, without the Rs cap sounds lower but incredible clear than the Rs cap.

To use Hypno both rails + I only have to change the polarity caps & use in both rails the same BC550C instead BC560C for Q3?

 

[Salas]

You can't use Hypno both sides + as it is.

 

[merlin el mago]

 

[merlin el mago]

You can't use Hypno both sides + as it is.

So for two + rails I need two Hypnos

 

[Salas]

Why don't you make a double + with remote p2p now that you got the knack of it, and make a pcb +/- needed somewhere else not to hack that nice board and make mistakes? Or even better make one real Hypno buffer to use somewhere, its very nice quality many builders say.

 

[merlin el mago]

Good idea Salas, I do mine own p2p with two positive rails with Rs to feed the Buffalo II & The Metronome. For diodes what kind do you mind will be better the Stealth or the MUR120?

 

[Salas]

Stealth.

 

[merlin el mago]

I only have on hand leds 1.8V:

CCS
Vout +5.5V will be 3 leds 1.8V = 5.4V?
Vout +7.5V will be 4 leds 1.8V = 7.2V?
Vout +-15VDC will be 8 leds 1.8V = 14.V?
Vout +-24V will be 13 leds 1.8V = 23.4V?

For Vref always 3 leds 1.8V?

 

[Salas]

No, it goes vice versa. CCS are always 3 leds. Vref is more leds. Vref=0.6V+what leds give when added.

 

[merlin el mago]

VRef 0.6V + leds:
Vout +5.5V 2 leds 1.8V = 4.2V?
Vout +7.5V 3 leds 1.8V = 6V?
Vout +-15VDC 8 leds 1.8V = 15V?
Vout +-24V will be 13 leds 1.8V = 24V?

For CCS D1+D2+D3 always 3 leds 1.8V?

 

[merlin el mago]

Or even better make one real Hypno buffer to use somewhere, its very nice quality many builders say.

YES I can try to use with buffer for the Buffalo II instead the IVY III or the passive I/V (parallel resistor 200R + series capacitors 4.7uF), only need to buy few components surely I will buy togheter the JG headamp.

 

[merlin el mago]

Why don't you make a double + with remote p2p now that you got the knack of it, and make a pcb +/- needed somewhere else not to hack that nice board and make mistakes? Or even better make one real Hypno buffer to use somewhere, its very nice quality many builders say.

VRef 0.6V + leds:
Vout +5.5V 2 leds 1.8V = 4.2V?
Vout +7.5V 3 leds 1.8V = 6V?
Vout +-15VDC 8 leds 1.8V = 15V?
Vout +-24V will be 13 leds 1.8V = 24V?

For CCS D1+D2+D3 always 3 leds 1.8V?

Instead leds Borbely uses:

VRef
LM329DZ TO-92/6.95V Low-noise buried Zener ref.
LM336Z-2.5 TO-92/2.5V Ref. Diode
LM336Z-5.0 TO-92/5.0V Ref. Diode
LM4040DIZ-10 TO-92/10V Ref. Diode

CCS
E-102 0.88-1.32mA Constant current diode
E-202 1.68-2.32mA Constant current diode
E-452 3.90-5.10mA Constant current diode
E-562 5.00-6.50mA Constant current diode
E-103 8.00-12.00mA Constant current diode

Leds are less noisy than these diodes?

 

[Salas]

One red LED with a Jfet is 35nVsqHz and adds non linearly under square rt rule (rms sum uncorrelated) with population. IR LED can be a bit less. LEDS are matching the JFET impedance well to be less inclined to pick up hum fundamentals.
LM329DZ can be more than 110nVsqHz. Its stiff due to low impedance too.
For any CCS LM depends on what it drives.

 

[merlin el mago]

So it's better if I use leds for Vref:

VRef 0.6V + leds:
Vout +5.5V 2 leds 1.8V = 4.2V?
Vout +7.5V 3 leds 1.8V = 6V?
Vout +-15VDC 8 leds 1.8V = 15V?
Vout +-24V will be 13 leds 1.8V = 24V?

For CCS D1+D2+D3 always 3 leds 1.8V or wich constant current diode can be used? so I can try to see if there is any difference between the constant current diodes or leds for CCS.

While please let me know if it's ok the leds quantities for VRef & CCS?

 

[Salas]

Example 5.5V. If your Leds are actually 1.8V when 5mA-6mA is running, you would need 2 LEDS + 2 1N4xxxx diode. 4.2 from Leds + 1.3 from diodes + 0.6 standard because in those circuits Vref it is Vbe lifted. In the DAC end they use just 2 leds and a small trimmer so to get the main Voltage from LEDS and add some controlled from the trimmer drop. You got to both understand the logic and make experiments.

There is lowest noise 2SK Jfet CCS for the LEDS already. Can't recommend CCS diodes since I haven't put them there.

 

[merlin el mago]

Sorry Salas, English isn't mine native language so is possible that don't explaint me very well.

I understand that in QuangHao shunt for DAC the Vref it is Vbe lifted.

If I understand well I need to add 2 1N4xxxx (please tell me exact number, remember I'm newbie be patient) diode to reach the 5.5Vout, so each 1N4xxxx adds 0.65V, but I don't understand 2 LEDS 1.8V x 2 = 3.6V & you said 4.2V

 

[Salas]

3.6+1.3+0.6=5.5V so 4.2 must have been a typo.

All those are V1.0 for different purposes. I designed that also when they were asking for 5V digital reg, then they liked it and made its way in a GB.

I would advise you to follow that route, i.e. build the most Voltage by LEDS and use a trimmer to add the last part so you can easily match. Because in practice, LEDS and diodes and Vbe will be needing many iterations to match. Diodes are nearly as quiet as LEDS.

 

[jims]

I think 1n4148 should be fine, there were some noise mearsurements on LEDs, zeners and the like, and the 1n4148 looked good between 5-20mA. Slightly lower noise as the current went up.

JimS

 

[merlin el mago]

3.6+1.3+0.6=5.5V so 4.2 must have been a typo.

All those are V1.0 for different purposes. I designed that also when they were asking for 5V digital reg, then they liked it and made its way in a GB.

I would advise you to follow that route, i.e. build the most Voltage by LEDS and use a trimmer to add the last part so you can easily match. Because in practice, LEDS and diodes and Vbe will be needing many iterations to match. Diodes are nearly as quiet as LEDS.

Ok now I understand, the trimmer always 100R will be enough for all voltages?

 

[merlin el mago]

I think 1n4148 should be fine, there were some noise mearsurements on LEDs, zeners and the like, and the 1n4148 looked good between 5-20mA. Slightly lower noise as the current went up.

JimS

Thanks JimS