[sdiy] There is no fun analogue chips anymore!

Veronica Merryfield veronica at merryfield.ca
Wed Jun 27 02:25:01 CEST 2012


Whilst the 741 is not a CA3080 replacement, has anyone tried using the two offset null pins (1 and 5) for gain control? I would think a common collector to the two pins might have some effect although the transfer function might be a little odd. Just a thought.

On 2012-06-26, at 1:48 PM, Jim Patchell wrote:

> A Trans-conductance Amplifier refers to the fact that the amplifier has a voltage input and a current output.  So, a 741 (voltage in-voltage out amp) can be turned into a transconductance amplier with the clever use of feed back resistors.  However, what we refer to as an O TA also has an input that will control the gain (transconductance) of the amplier.  So, NO, in general, you cannot use a 741 to replace a CA3080.
> 
> -Jim
> 
> On 6/25/2012 12:43 PM, Pete Hartman wrote:
>> This is a TOTAL newb question, but...  I've seen at least one
>> implementation of an alleged transconductance amplifier using a 741 as
>> the base (but not used in synths).  IF you can explain in a paragraph
>> or two, I'm curious why that sort of thing is not used more generally
>> given the relative scarcity of the dedicated OTAs.  And if my question
>> exhibits a level of ignorance that can't be addressed on list, then
>> feel free to ignore me (or send me links for research) too :-D
>> 
>> Pete
>> 
>> On Mon, Jun 25, 2012 at 2:36 PM, Jim Patchell <patchell at cox.net> wrote:
>>> Heck...I  would be happy if they would just bring back an OLD OTA! (like the
>>> CA3280).
>>> 
>>> -Jim
>>> 
>>> 
>>> On 6/25/2012 12:04 PM, KD KD wrote:
>>>> There is no fun analogue chips anymore!
>>>> 
>>>> It's all OPamp's, on and on and on and on!
>>>> Not even ONE single new OTA!
>>>> 
>>>> Thank's for stealing 5 sec of your valuable time with this rant! :)
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> 
> 
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