[sdiy] Modelling the LM13700 bias input in LTSpice

[sleepy_dog at gmx.de]

Ha! I just read "bias", and then a cognitive bias crept in and bent it 
to "diode bias", because that was the last thing I was having trouble 
with, so *obviously* that's the only thing you could have meant ;-) 
Since I don't have a cognitive bias pin that I could ground or whatever, 
this will happen again.

Am 13.08.2017 um 18:34 schrieb Tom Wiltshire:
> Thanks Steve. That seems to do the trick, although I still don’t know what the details are.
>
> When I said “bias input”, I mean the Iabc control input, not the diode bias. I’m not using the diode bias in this circuit, so currently that’s not an issue.
>
> Thanks,
> Tom
>
> ==================
>         Electric Druid
> Synth & Stompbox DIY
> ==================
>
>> On 13 Aug 2017, at 13:43, sleepy_dog at gmx.de wrote:
>>
>>
>> I don't recall *exatcly* where I found this, I think in the depths of the LTspice yahoo group.
>> Uploaded here (they'll delete it in 1..2 weeks I think, so If anyone gets from vacation and reads this then, sorry ;) )
>> https://we.tl/Vpnte54SiJ
>>
>> I used it in some tests and it basically worked as I (an electronics layman picking up some things here and there)
>> expected. *Except* exactly when doing anything with the diode bias pin. But perhaps I just haven't understood properly how to use it exactly, with regards to what that does to the overall behavior of the OTA except "make it more linear".
>> Maybe you have more "luck" with that ;)
>>
>> Steve
>>
>>
>> Am 13.08.2017 um 12:29 schrieb Tom Wiltshire:
>>> Hi All,
>>>
>>> If I want to do some experiments in simulation, using different current sources to feed the pin1/16 bias input of the LM13700, how should I model the 13700’s input?
>>>
>>> I don’t particularly need to model the whole chip, but I need the input to respond realistically. If modelling the whole chip is the best way, where do I find a good LM!34700 model? I’ve read various places that the input is two diode drops above the negative power rail, and other places that it’s a diode drop above ground. And what about its impedance? What does that look like?
>>>
>>> Thanks,
>>> Tom
>>>
>>>
>>> ==================
>>>         Electric Druid
>>> Synth & Stompbox DIY
>>> ==================
>>>
>>>
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