Zener regulator : load and zener current

Started by Anonymous in sci.electronics.design4 years ago 43 replies

In the simple zener regulators like the one below, If the load current is 1= 00ma and zener current is 10ma we calculate the resistor to allow...

In the simple zener regulators like the one below, If the load current is 1= 00ma and zener current is 10ma we calculate the resistor to allow 110ma. If Vin is above Vz and the load draws 50ma, the remaining 60ma flows throug= h zener. What makes it that the remaining current after the load current go= through the zener? Whay can't it be the otherway? i.e after the zener curr= ent the rema...


Zener Diode Protection

Started by john1987 in sci.electronics.design6 years ago 48 replies

Hi, I need to protect the inout of the following DC to DC converter http://cds.linear.com/docs/Datasheet/3970fa.pdf I choose the...

Hi, I need to protect the inout of the following DC to DC converter http://cds.linear.com/docs/Datasheet/3970fa.pdf I choose the following zener diode http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MAZ43900MFCT-ND I put the zener between the positive input and ground of the chip but as soon as I increase the DC voltage above 40 volts it get burned. Is the zener ...


Zener clamping output of regulator

Started by panfilero in sci.electronics.design4 years ago 23 replies

Hello, If I had a little isolated 3.3V voltage regulator like this guy http://www.recom-power.com/pdf/Econoline/RM.pdf and I put a 3.3V...

Hello, If I had a little isolated 3.3V voltage regulator like this guy http://www.recom-power.com/pdf/Econoline/RM.pdf and I put a 3.3V zener right across the output to clamp the output to 3.3V like this zener http://www.diodes.com/datasheets/ds30410.pdf but I saw 3.6V across my zener.... any thoughts on what is going on? is it not cool to put a zener at the output to clamp the ...


TVS used as a zener

Started by mook johnson in sci.electronics.design8 years ago 10 replies

Can a 1.5KE series TVS be used as a zener with a dC bias. Sat I have a circuit that is fed by a 50mA current source that on fault conditions...

Can a 1.5KE series TVS be used as a zener with a dC bias. Sat I have a circuit that is fed by a 50mA current source that on fault conditions pulses up to 500mA for ~10mS. The circuit needs to clamp at between 33 and 40V. I have a 36V 1.5KE already in the circuit for transient protection of a 30V line elsewhere but was wondering if I could use the same part for this zener application. ...


zener diode pulse current rating

Started by panfilero in sci.electronics.design6 years ago 25 replies

I need a 30V zener to drop the a high voltage of 100V down to 60V so I can use it with a switch mode power supply chip. So while this circuit...

I need a 30V zener to drop the a high voltage of 100V down to 60V so I can use it with a switch mode power supply chip. So while this circuit is in use the zener will be exposed to current pulses from the switching, these current pulses are in the neighborhood of 1A. I've gone to digikey and pulled up some zeners but I don't see this rating, where can I find the rating that tells me whether...


Zener kinda turns on

Started by panfilero in sci.electronics.design5 years ago 145 replies

I was making a circuit that when you power it up with 5V a 5V LED indicator= turns on and if you power it up with 12V the 5V LED goes off and...

I was making a circuit that when you power it up with 5V a 5V LED indicator= turns on and if you power it up with 12V the 5V LED goes off and the 12V i= ndicator goes on. But... it's not coming on with 5V...=20 I spiced it, and it doesn't work in simulation either... if you look at the image on the link I put a 5.6V zener D1 in the circuit thinking that this Zener would be OFF = un...


The central limit theorem rocks, (summing Zener noise)

Started by George Herold in sci.electronics.design7 years ago 32 replies

So the following is the result of a previous thread where John Larkin suggested that one way to get rid of the voltage asymmetry in a...

So the following is the result of a previous thread where John Larkin suggested that one way to get rid of the voltage asymmetry in a Zener noise source was to sum a whole bunch together. I was initially doubtful, but thought I should do the experiment. I had a whole bunch (five) of lockins to test today. They have a build in Zener noise source with terrible asymmetry. So I summed them w...


Zener Diode Selection

Started by Anonymous in sci.electronics.design5 years ago 4 replies

Hi, DC to DC Converter:=20 http://cds.linear.com/docs/Datasheet/3970fb.pdf Zener...

Hi, DC to DC Converter:=20 http://cds.linear.com/docs/Datasheet/3970fb.pdf Zener Diode:=20 http://www.digikey.com/product-detail/en/1N5364B-TP/1N5364BTPMSCT-ND/111430= 6 The DC to DC converter can handle input voltage upto 40V. DC to DC convert= er is configured to output 5V. I do not want the input voltage to exceed 33= Volts. That is why I am using a 33V Zener. But I think that...


Zener noise source (freq < 1MHz.)

Started by George Herold in sci.electronics.design6 years ago 12 replies

Zener noise source (freq < 1MHz.) I was revisiting Zener's as noise sources today. I first tried some 12V (1W*) diodes. (I want to bias them...

Zener noise source (freq < 1MHz.) I was revisiting Zener's as noise sources today. I first tried some 12V (1W*) diodes. (I want to bias them from 15V rails.) They worked fine, but I found the noise varied by at least 6dB (a factor of 2 in V peak) for different diodes from the same strip. (After testing 5 I gave up.) So I fell back to an old circuit. +15--+----+ Z | ^


Zener diode below-threshold reverse current

Started by Tim Wescott in sci.electronics.design1 year ago 271 replies

I know the theory, more or less. In practice, what's the reverse current through a zener diode at levels well below the breakdown voltage? ...

I know the theory, more or less. In practice, what's the reverse current through a zener diode at levels well below the breakdown voltage? I've got a circuit where I'm feeding a 12V linear regulator with a 25V line. It would be handy to put a zener diode in there so that when the 25V line drops to 4V the current into the regulator drops to tens of microamps. I'm wondering if a series...


Minimum current for zener diodes

Started by Sonnich Jensen in sci.electronics.design5 years ago 32 replies

Hi What is the minimum current for a zener, such as BZX55/C5V6 to work properly? I tried using 500uA, but it does not seem good. I looks like...

Hi What is the minimum current for a zener, such as BZX55/C5V6 to work properly? I tried using 500uA, but it does not seem good. I looks like less than 1mA is not enough, more like 2mA. Sonnich


Zener-noise (current)

Started by Bosken in sci.electronics.design8 years ago 9 replies

Hi all, I have made a noise generator based on a zener diode. But I want to know how the noise reacts when I increase the current through de...

Hi all, I have made a noise generator based on a zener diode. But I want to know how the noise reacts when I increase the current through de zener diode. With PSpice a simulated the circuit and it seems when the current increased, sigma (RMS voltage) decreases.. But when I do the practical test, it seems when the current increased, sigma (RMS voltage) also increased.. Does anyone have...


what I would use for a low current 100Volt supply.

Started by Jamie in sci.electronics.design6 years ago 12 replies

This is my contributions to the already going thread on a 100 volt capable DC-DC buck boost using a 555 and a zener for regulation that uses the...

This is my contributions to the already going thread on a 100 volt capable DC-DC buck boost using a 555 and a zener for regulation that uses the minimum parts. I don't even have a timing cap in there. Set R1 for the Max I you need as the load and the zener will suck up what you don't use to maintain a constant voltage.. Of course this type of boost is only good if your load constraints ar...


abusing transistors

Started by John Larkin in sci.electronics.design8 years ago 19 replies

Thought I'd zener some NPN b-e junctions. The mode is to use the collector and emitter, base open, putting a zenered e-b junction in series with...

Thought I'd zener some NPN b-e junctions. The mode is to use the collector and emitter, base open, putting a zenered e-b junction in series with the forward-biased c-b junction, "reference zener" style. BFT25 gives only 3.02 volts at 1 mA, with about 0.6 of that being c-b drop. BFS17 is 3.78, 0.53 of that c-b drop. Those are RF transistors. A more conventional BCX70 is 8.08 volts at...


Zener diode modeling

Started by Robert Baer in sci.electronics.design6 years ago 36 replies

Say one takes an E-B junction of a transistor or other diode and measures the (reverse) breakdown voltage over a wide range of currents...

Say one takes an E-B junction of a transistor or other diode and measures the (reverse) breakdown voltage over a wide range of currents (say 5nA to 5mA), and assume there is no point or range where one sees characteristics of negative resistance or of oscillation. Also say that voltage is about 9 volts. Q: is that zener or avalanche breakdown? Q: how does one make a SPICE mode...


Voltage source with Low Quiescent and No Minimum Load

Started by rich in sci.electronics.design5 years ago 4 replies

I need to provide a backup voltage to a device, the current requirement is = 20uA. The device is battery powered. It is my understanding that...

I need to provide a backup voltage to a device, the current requirement is = 20uA. The device is battery powered. It is my understanding that zener re= gulator requires enough current to put the zener into regulation which woul= d be too much for our battery life. I know there are voltage references out there for this but they all seem to= be in the $2 range, a bit pricey. Any elegant...


Fast zener diode substitute

Started by Yvan in sci.electronics.design8 years ago 28 replies

I decided to built this: http://notes.ump.edu.my/fkee/e-Magazine/Elektor%202004/Articles/E/e04b020.pdf It keeps the battery a little bit...

I decided to built this: http://notes.ump.edu.my/fkee/e-Magazine/Elektor%202004/Articles/E/e04b020.pdf It keeps the battery a little bit active, preventing sulphation by loading the battery with a hefty current (40 A) for a short interval (50 ?s) approximately every two minutes. But they used a fast zener diode (BZT03 27V) across the FET for protection, as rather large voltage spikes


Again with a power supply input protection

Started by George Herold in sci.electronics.design1 year ago 12 replies

A circuit will have 24V @ 1.5A (max) input from a wall wart. I'd like to design in reverse polarity and maybe over voltage input protection. ...

A circuit will have 24V @ 1.5A (max) input from a wall wart. I'd like to design in reverse polarity and maybe over voltage input protection. (There are lots of threads about this.) I don't like the Zener/ polyfuse idea, cause there is going to be a lot of power in the Zener... I'm afraid it will smoke before the polyfuse lets go. So some FET circuit. Here's Jim T's offering. (fro...


minimum zener current for break down.

Started by Anonymous in sci.electronics.design5 years ago 18 replies

Is there any minimum zener current required for it to break down or is it o= nly dependent on voltage? For example, MMSZ5V1T1G (datasheet below)...

Is there any minimum zener current required for it to break down or is it o= nly dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break d= own voltage Izt1 is given at test condition as 5ma. The following is our application and current should be limited to the volta= ge sensing circuitry to less than 100uA. So after break down voltage of 5.6= V, only few tens of uA will flow ...


Dealing with mains power transients

Started by Sylvia Else in sci.electronics.design1 year ago 19 replies

I'm looking at protecting a power sense circuit from mains power transients, using a resistor and a zener diode. Spice says it works well,...

I'm looking at protecting a power sense circuit from mains power transients, using a resistor and a zener diode. Spice says it works well, but when the zener conducts, essentially the entire transient voltage appears across the resistor. A high voltage transient spike is likely to be very narrow, but I can find nothing to say I can put, say, 5000V, across a 1K resistor, even for a micro...