Forums

Zenering a big transistor

Started by George Herold June 26, 2017
On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote:
> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: > > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > > There's a couple of depletion fets in series as current limiters. (LND150) > > The b-e junction starts to zener at ~30 V (only two tested so far). > > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > > Will it take time? I'm going to measure forward voltage again after > > zenering for 15 minutes. Should I measure something else too? > > > > TIA > > > > George H. > > Why not just protect your TIP31C from zenering? A few diodes would do it. >
e.g., | +----. | | TIP31C |<' --- .---| ^ D1 | |\ | | | | '-----+----' | | Add a zener in series with D1 if you need to stand off some reverse voltage. Cheers, James Arthur
George Herold wrote:
> I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > There's a couple of depletion fets in series as current limiters. (LND150) > The b-e junction starts to zener at ~30 V (only two tested so far). > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > Will it take time? I'm going to measure forward voltage again after > zenering for 15 minutes. Should I measure something else too? > > TIA > > George H.
It appears that zenering any junction causes dislocations that act like ionic contamination and like radiation damage. Like radiation damage, the accumulation is total dose related, and can be annealed out. A larger current is just like a higher radiation level; a one-to-one correspondence.
On Monday, June 26, 2017 at 1:04:43 PM UTC-4, dagmarg...@yahoo.com wrote:
> On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: > > On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: > > > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > > > There's a couple of depletion fets in series as current limiters. (LND150) > > > The b-e junction starts to zener at ~30 V (only two tested so far). > > > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > > > Will it take time? I'm going to measure forward voltage again after > > > zenering for 15 minutes. Should I measure something else too? > > > > > > TIA > > > > > > George H. > > > > Why not just protect your TIP31C from zenering? A few diodes would do it. > > > > e.g., > | > +----. > | | > TIP31C |<' --- > .---| ^ D1 > | |\ | > | | | > '-----+----' > | > | > > Add a zener in series with D1 if you need to stand off some reverse voltage. > > Cheers, > James Arthur
Right, I thought of that. (Another part.) I was thinking of an LED, less leakage... I don't know if I care about leakage or not... probably not, 10/100 uA of bias current. George H.
On Mon, 26 Jun 2017 09:40:43 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Monday, June 26, 2017 at 12:32:13 PM UTC-4, John Larkin wrote: >> On Mon, 26 Jun 2017 08:51:41 -0700 (PDT), George Herold >> <gherold@teachspin.com> wrote: >> >> >I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >> >There's a couple of depletion fets in series as current limiters. (LND150) >> >The b-e junction starts to zener at ~30 V (only two tested so far). >> >So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >> >Will it take time? I'm going to measure forward voltage again after >> >zenering for 15 minutes. Should I measure something else too? >> > >> >TIA >> > >> >George H. >> >> Why are you ever zenering the poor thing? >> >> You'll have to measure temperature accurately, too, to see if zenering >> is affecting the junction tempco. Or compare the drop of two >> transistors, one that you zener and one that you don't. >> >> But TIP31C is an NPN. NPNs tend to zener BE at lower voltages than >> PNPs. Usually. >> >> >> -- >> >> John Larkin Highland Technology, Inc >> >> lunatic fringe electronics > >Oh snap, sorry tip32C. (I'm always mixing things up.) >I'm only zenering it to see if my over voltage protection works. >Maybe I'll need some other diode for protection... an LED? > >George H.
Why not a resistor? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

>On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >> > There's a couple of depletion fets in series as current limiters. (LND150) >> > The b-e junction starts to zener at ~30 V (only two tested so far). >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >> > Will it take time? I'm going to measure forward voltage again after >> > zenering for 15 minutes. Should I measure something else too? >> > >> > TIA >> > >> > George H. >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. >> > >e.g., > | > +----. > | | >TIP31C |<' --- > .---| ^ D1 > | |\ | > | | | > '-----+----' > | > | > >Add a zener in series with D1 if you need to stand off some reverse voltage. > >Cheers, >James Arthur
Or use the c-b junction instead. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Mon, 26 Jun 2017 09:11:21 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

>George Herold wrote: >> I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >> There's a couple of depletion fets in series as current limiters. (LND150) >> The b-e junction starts to zener at ~30 V (only two tested so far). >> So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >> Will it take time? I'm going to measure forward voltage again after >> zenering for 15 minutes. Should I measure something else too? >> >> TIA >> >> George H. > It appears that zenering any junction causes dislocations that act >like ionic contamination and like radiation damage. > Like radiation damage, the accumulation is total dose related, and >can be annealed out. > > A larger current is just like a higher radiation level; a one-to-one >correspondence.
Reference zeners are stable to parts per million for years. There's something special about the b-e junction of a transistor. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Mon, 26 Jun 2017 10:17:20 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

[snip]
> >Reference zeners are stable to parts per million for years. There's >something special about the b-e junction of a transistor.
Really? How come beta degrades when a b-e junction is used as a zener? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box... producing elegant solutions.
On Monday, June 26, 2017 at 9:37:09 AM UTC-7, George Herold wrote:

> ...the diode connected transistor seems to give a more consistent* > temperature sensor than just the C-B or E-B junction. It's not something > I looked at very closely, and maybe just a fluke with the TIP31.
> *by consistent I mean that I measured one set of curves (V vs T) for the > diode and curves for all other diodes were the same, except for an offset, which was proportional with temperature.
Probably this is due to base spreading resistance. The TIP32C part number indicates (the 'C' part) high breakdown voltage (collector-base); the 'B' and 'A'' parts were lower rated. So, there's significant manufacturing range in these parts' characteristics, and that particular characteristic goes with the base doping level, i.e. base material resistivity. When using C-B or E-B diodes, the (thin, lighter-than-emitter-doped) base adds a bit of electrical resistance. The E-(B+C) connection, in forward bias, has only a fraction of the base current that an E-B connection does, so the base's resistance adds a couple of orders of magnitude lower voltage drop.
On 06/26/2017 01:17 PM, John Larkin wrote:
> On Mon, 26 Jun 2017 09:11:21 -0800, Robert Baer > <robertbaer@localnet.com> wrote: > >> George Herold wrote: >>> I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >>> There's a couple of depletion fets in series as current limiters. (LND150) >>> The b-e junction starts to zener at ~30 V (only two tested so far). >>> So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >>> Will it take time? I'm going to measure forward voltage again after >>> zenering for 15 minutes. Should I measure something else too? >>> >>> TIA >>> >>> George H. >> It appears that zenering any junction causes dislocations that act >> like ionic contamination and like radiation damage. >> Like radiation damage, the accumulation is total dose related, and >> can be annealed out. >> >> A larger current is just like a higher radiation level; a one-to-one >> correspondence. > > Reference zeners are stable to parts per million for years. There's > something special about the b-e junction of a transistor.
I'd guess that the larger size and higher doping of the emitter region means that the potential barrier generated by reverse biasing the junction is too wide for thermally-generated minority carriers to quantum tunnel through, they can only cross via avalanche breakdown
On Mon, 26 Jun 2017 10:41:49 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Mon, 26 Jun 2017 10:17:20 -0700, John Larkin ><jjlarkin@highland_snip_technology.com> wrote: > >[snip] >> >>Reference zeners are stable to parts per million for years. There's >>something special about the b-e junction of a transistor. > >Really? How come beta degrades when a b-e junction is used as a >zener? > > ...Jim Thompson
Beats me. But reference zeners are super stable, usually in the 5-10 mA range, for years. There are also "reference transistors" (or "reference amplifiers") which are, I think, an NPN transistor with a separate zener in series with its emitter. Fluke used them in their differential voltmeters, which are damned accurate for decades. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com