Thoma
Guest
Tue Jan 17, 2012 11:09 am
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Bill Sloman
Guest
Tue Jan 17, 2012 2:25 pm
On Jan 17, 10:09 am, Thoma <thoma.h...@gmail.com> wrote:
Quote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Try comparing guaranteed leakage currents. You can buy low leakage
diodes, but they tend to be more expensive than jelly-bean transistors
--
Bill Sloman, Nijmegen
George Herold
Guest
Tue Jan 17, 2012 4:56 pm
On Jan 17, 4:09 am, Thoma <thoma.h...@gmail.com> wrote:
Quote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_and_clamping_techniques.php
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
John Larkin
Guest
Tue Jan 17, 2012 7:25 pm
On Tue, 17 Jan 2012 06:56:37 -0800 (PST), George Herold
<gherold_at_teachspin.com> wrote:
Quote:
On Jan 17, 4:09 am, Thoma <thoma.h...@gmail.com> wrote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_and_clamping_techniques.php
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
The c-b junction of a BFT25 leaks roughly 20 fA at room temp. It's
tricky to measure.
John
miso
Guest
Tue Jan 17, 2012 11:22 pm
On 1/17/2012 6:56 AM, George Herold wrote:
Quote:
On Jan 17, 4:09 am, Thoma<thoma.h...@gmail.com> wrote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_and_clamping_techniques.php
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
You probably want to do the EB short. Floating anything is a bad idea,
and high fields lead to junction damage which will surely leak.
Generally when you ESD test a chip, you keep zapping until you see
junction damage. This sets a "known quantity" on how much the device can
take. [It isn't exactly kosher since you do multiple tests on the same
pin and often go test another pin after zapping an adjacent pin.]
However, you also zap a rail at your factory spec and run them through
ATE, just to insure nothing bad happened internally.
Robert Baer
Guest
Wed Jan 18, 2012 9:52 am
miso wrote:
Quote:
On 1/17/2012 6:56 AM, George Herold wrote:
On Jan 17, 4:09 am, Thoma<thoma.h...@gmail.com> wrote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_and_clamping_techniques.php
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
You probably want to do the EB short. Floating anything is a bad idea,
and high fields lead to junction damage which will surely leak.
Generally when you ESD test a chip, you keep zapping until you see
junction damage. This sets a "known quantity" on how much the device can
take. [It isn't exactly kosher since you do multiple tests on the same
pin and often go test another pin after zapping an adjacent pin.]
However, you also zap a rail at your factory spec and run them through
ATE, just to insure nothing bad happened internally.
What is far better, is to measure the NF before and after ONE test.
Betcha the results will raise your eyebrows and swear off multiple
testing like that..
Thoma
Guest
Wed Jan 18, 2012 10:44 am
On Jan 17, 3:56 pm, George Herold <gher...@teachspin.com> wrote:
Quote:
On Jan 17, 4:09 am, Thoma <thoma.h...@gmail.com> wrote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_a...
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
Hi George,
Many thanks.
It is exactly this article I search for.
Regards,
Thoma
George Herold
Guest
Wed Jan 18, 2012 4:10 pm
On Jan 17, 1:25 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Tue, 17 Jan 2012 06:56:37 -0800 (PST), George Herold
gher...@teachspin.com> wrote:
On Jan 17, 4:09 am, Thoma <thoma.h...@gmail.com> wrote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_a...
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
The c-b junction of a BFT25 leaks roughly 20 fA at room temp. It's
tricky to measure.
John- Hide quoted text -
- Show quoted text -
I found something like a few pA for a 2n3904. But the opamp leakage
was also ~ 10pA so that was about my limit.
George H.
George Herold
Guest
Wed Jan 18, 2012 4:20 pm
On Jan 17, 5:22 pm, miso <m...@sushi.com> wrote:
Quote:
On 1/17/2012 6:56 AM, George Herold wrote:
On Jan 17, 4:09 am, Thoma<thoma.h...@gmail.com> wrote:
Hi all,
To build limiters that protect my analog input stages, I use for years
the base-collector junction of transistors instead of simple diodes.
This improves the SNR (the base-collector junction seems less noisy
than the diode junction).
It has become a reflex and now I am not able to find the justification
again.
And unfortunately, I did not found anything on this subject.
Does anyone have an application note on the subject or just a better
memory than mine?
Thank you in advance
Thoma
Yeah, much lower leakage currents. This is a nice article,
http://www.edn.com/blog/Designing_Ideas/41356-Bob_Pease_on_bounding_a...
George H.
(If the link doesn't work, then search for EDN +bounding and clamping)
You probably want to do the EB short. Floating anything is a bad idea,
and high fields lead to junction damage which will surely leak.
Hmm, I left the emitter floating. (That's the way Bob P. drew it.)
Does shorting EB change anything?
Quote:
Generally when you ESD test a chip, you keep zapping until you see
junction damage. This sets a "known quantity" on how much the device can
take. [It isn't exactly kosher since you do multiple tests on the same
pin and often go test another pin after zapping an adjacent pin.]
However, you also zap a rail at your factory spec and run them through
ATE, just to insure nothing bad happened internally.- Hide quoted text -
I tested the ESD protection on our diode laser by first scuffing up a
big charge and touching things.
I then got this piezo sparker from a butane lighter and zapped it with
that. (both polarities.)
Watching the laser diode output you could see little spikes in the
light if any charged leaked in.
ESD damage also tended to 'wonk' the wavelength a little.
George H.
Quote:
- Show quoted text -
