## Zener regulator : load and zener current

Started by in sci.electronics.design8 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 clamping output of regulator

Started by in sci.electronics.design8 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 ...

## zener question

Started by in sci.electronics.design4 years ago 21 replies

I have an early version of a ham radio mobile supply that can't take more than 14.5 volts. Later versions used different transistors good to...

I have an early version of a ham radio mobile supply that can't take more than 14.5 volts. Later versions used different transistors good to 16v that sell for big \$. Could I wire in a 14.something-small zener to a big power resistor to gnd - and if so would it cost less what size of zener and resistor would the panel suggest

## zener diode pulse current rating

Started by in sci.electronics.design10 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 in sci.electronics.design9 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...

## Zener Diode Selection

Started by in sci.electronics.design9 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 in sci.electronics.design10 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 | ^

## fast, small low-capacitance zener to protect MOSFET gates

Started by in sci.electronics.design3 years ago 28 replies

I became discouraged of finding a suitable low-capacitance zener to protect the MOSFET gates in my high-voltage amplifier designs. (The...

I became discouraged of finding a suitable low-capacitance zener to protect the MOSFET gates in my high-voltage amplifier designs. (The protection may be optional, but one sleeps better with it in place.) Even the 50uA-rated low-current zener diodes are in fact larger-die types, with high capacitance. For example, the 7.5-volt MMSZ4693 has about 130pF at zero volts. My solution was to us...

## Fet G-S zener

Started by in sci.electronics.design3 years ago 10 replies

Well I just blew out the G-S junction of a fet. I'm going to redesign circuit a bit... but I was also thinking of adding a ~15V G-S zener....

Well I just blew out the G-S junction of a fet. I'm going to redesign circuit a bit... but I was also thinking of adding a ~15V G-S zener. (V_GS max = +/- 20 V) Is there any downside I should think about? I guess I'd need some sort of current limit. (Resistor at a minimum) George H.

## Zener diode below-threshold reverse current

Started by in sci.electronics.design5 years 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 in sci.electronics.design9 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

## LTspice Zener Models

Started by in sci.electronics.design2 years ago

I'm looking to model a circuit with a zener diode in it and the exact part doesn't seem to have a simulation model. Looking at the 11 choices in...

I'm looking to model a circuit with a zener diode in it and the exact part doesn't seem to have a simulation model. Looking at the 11 choices in LTspice I see a variety of parameters. The one that I'd probably want to match the most closely is the source resistance, Rs. This seems to be a very difficult number to pin down. The part in question is CZRU52C6V2 by Comchip. They l

## Abusing brick on the rope

Started by in sci.electronics.design3 years ago 50 replies

Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been...

Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm resistor in series. (the zener stops it from turning on if one of the rails fails.) It j...

## Zeners in Series

Started by in sci.electronics.design2 years ago 80 replies

Whilst mere hobbyists like myself can easily get away with making up a desired zener value from putting two smaller value ones in series to add...

Whilst mere hobbyists like myself can easily get away with making up a desired zener value from putting two smaller value ones in series to add together their rated voltages, can such a dodge be employed by professional designers without losing face? I mean, in the case where there is no commercially available zener with precisely the desired breakdown voltage? Would a pro designer be op...

## Zener turn-on question

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

I was playing around with the CD4093 boost converter circuit someone posted a while back: What's the point in simulate, it's simple...

I was playing around with the CD4093 boost converter circuit someone posted a while back: What's the point in simulate, it's simple enough that I can just "simulate" on a breadboard. Related questions: there's some relation between the Zener quiescent current, the inductor DCR, max output current, and number of sec

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

Started by in sci.electronics.design10 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...

## Zener diode modeling

Started by in sci.electronics.design10 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 in sci.electronics.design9 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...

## Again with a power supply input protection

Started by in sci.electronics.design6 years 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 in sci.electronics.design9 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 ...