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That is a great way to remember electron flow, thanks Dave!! I was always thinking of the arrows and would confuse myself sometimes when thinking of electron flow. Either way is fine, just need to work your way through a circuit one way or another - by checking with the opposite method you can catch mistakes.well being old school taught we learnt to think of the diode symbol as like a speaker
and when you do that electron flow coming out the front of a speaker makes sense
Tonight's question!
Here is the schematic for producing a negative supply voltage from the datasheet. I assume that the ground symbol is true earth ground and not common.
1. Can someone confirm this for me. I am relatively sure of it.
2. Does this arrangement make more sense? Should the negative regulation work as shown?
in the case of a single supply rail, the Ti datasheet part page you posted is ok and the GND symbol is just your zero volt rail
the problem is when you try and incorporate that into a dual rail supply as you have, you no longer have a dual rail supply with the common 0V rail
you have 2 separate supplies and it cannot be used for a dual rail supply like what you are probably aiming for so that you can supply IC's that need a +V, 0V and -V rails
Valid points, I saw some information in the datasheet which led me to believe it was possible to do. Lack of experience brought me down this path, but at least I read the datasheet, LOL ;-)The final point being, They produce -V voltage regulators for a reason .... if you could easily produce dual rail supplies without them, what would be the point of manufacturing -V regulators ??
Dave
I didn't find a complementary chip, I think I will research negative v- regulators and use that as a starting point.
Thanks Dave, I will look at in depth.Well I did mention the LM333 in a post on page 2 .... its capable of 3A, to increase the current capability, you have 2 choices
1) a current pass transistor or
2) parallel 2 x LM333 's
either way will work
Dave
Thanks Dave, off I go!inefficiencies in this case isn't really a significant problem ... the system is mains powered
its when using linear reg's with battery supplies that one really starts worrying about the wasted power from the battery
if not well filtered, switching supplies can be noisy, ya just have to do your design well to take that into account
D
Thanks Dave, I will look at in depth.
Is the large amount of power wasted not really much concern with linear regulators?
Konstantine mentioned that linear is the way to go with bench supplies because there is less noise and that becomes very important with amplifiers, but the inefficiency leaves me questioning this approach.
I was thinking more along the lines of having to rid the IC of heat - specifically at the extremes of low voltage and high current.Well i used audio amplifiers as an example. in general Yes linear is the way to go if you are most interested in the quality of your psu's output. not to mention that the circuits are much more simple.
Why are you so concerned about losses within your psu ? It is really not a big deal since it is mains powerewd and think about it you will only be useing it for short time periods. (power up the psu, connect the device under test, run for a while then turn all off) after a year how many hours in total you think your psu will have run ?
Aside from just a heatsink, have you thought of using computer fans to assist the cooling?Yes normally that is indeed not a problem. Unless your power supply delivers high current like mine that uses 4x 2n3055 transistors and delivers up to 10 Amps. In that case you will need a really large heatsink !
Found out that the LM333 are obsolete. Digikey had a listing with "call" and TI's datasheet are marked obsolete.Well I did mention the LM333 in a post on page 2 .... its capable of 3A, to increase the current capability, you have 2 choices
1) a current pass transistor or
2) parallel 2 x LM333 's
either way will work
Dave
ooohhh bummerFound out that the LM333 are obsolete. Digikey had a listing with "call" and TI's datasheet are marked obsolete.
That one is also obsolete. I am looking at the LT1083 - 7.5A max, three terminal device. I haven't thoroughly searched yet, but the datasheet didn't seem to have anything about using the regulator as a negative supply. If I can not find a negative complement, there is a 5 pin LT1085/LT1185 +/- regulators that I can look at next.LT1033
Hi AK, I think I see what you mean in post #43 - the input of the negative regulator needs to be fed from the positive side of the bridge rectifier, while the output of the reg. is held to ground, this would leave the bottom rail to 'go more negative' as the regulator adjust to keep its Vref stable.Post #41, Figure 26 - look at the bridge.
ak