Re: Pspice transfer function

"Robert Baer" <robertbaer@xxxxxxxxxxxxx> schrieb im Newsbeitrag
news:EXole.854$MI4.769@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Helmut Sennewald wrote:
>
>> "Robert Baer" <robertbaer@xxxxxxxxxxxxx> schrieb im Newsbeitrag
>> news:Dcgle.591$IL3.180@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>
>>>Helmut Sennewald wrote:
>>>
>>>
>>>>"Robert Baer" <robertbaer@xxxxxxxxxxxxx> schrieb im Newsbeitrag
>>>>news:kfWke.6344$Lc1.6222@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>>
>>>>
>>>>> When i test the actual circuit, the output has a transition "hump"
>>>>> between the linear I/O part and the regulation part; it is about 900mV
>>>>> in amplitude.
>>>>> The Spice does not show it; why?
>>>>
>>>>Hello Robert,
>>>>Where did you uy the 1mA-current source?
>>>>Type:?
>>>>Manufacturer:?
>>>>
>>>>Is it just a schematic simplification?
>>>>Then please provide the real circuit(schematic) for this current source.
>>>>
>>>>Is this Z-diode in the real circuit or is this also some kind of
>>>>simplification for another device?
>>>>
>>>>Have you tried to replace this crrent source with a simple 33k resistor.
>>>>It would be very interesting how your real circuit behaves then
>>>>compared to the simulation.
>>>>
>>>>Best regards,
>>>>Helmut
>>>>
>>>
>>> The current source is a DMOSFET; the DN3545 and a 2.2K resistor.
>>> Do not know how to model that.
>>
>>
>> Hello Robert,
>>
>> You could try to find a SPICE model of a similar device
>> from another manufacturer.
>>
>>
>>> This was tested using an E-B transistor junction (in reverse) for the
>>> zener; the transistor type was selected to have no negative R effects
>>> and have low noize at all currents from nanoamps to milliamps.
>>> The "hump" mentioned was measured not only with meters, but also seen
>>> on a curve tracer.
>>
>>
>> That's it.
>> If you replace this "bad" device with a real Zener diode, the
>> problem should go away. It's a very very bad idea to use the
>> B-E breakdown as a Zener-diode for any serious application.
>>
>> I rate the whole thing not as a problem to find a SPICE
>> model for the B-E breakdown. It's simply a bad design
>> practice to use this B-E breakdown as a reference voltage.
>>
>> Best regards,
>> Helmut
> Sorry, this particular transistor E-B junction is superior to any zener
> diode i have seen. Furthermore, if i add in the B-C junction in forward
> mode, i get a voltage reference good to 180C.
> Furthermore, when i replace it with a UCC2801 (zeners near 13.5V), i see
> exactly the same thing.


Hello Robert,

Is this "bump" a dynamic behaviour when the inut voltage is ramped up
with a certain speed or is it also visible when you manually
increase the input voltage very slowly?

Means this "bump" a higher or a lower voltage?

Best regards,
Helmut


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