[sdiy] multiplier from three 741s?

[Dan Snazelle]

Neato 

I was just reading an old sdiy thread where somebody was throwing out the idea of using the 741 as a vc element
For a four pole Vcf  it sure would be a LOT of resistors ;) 

Sent from my iPhone

> On Nov 15, 2014, at 10:41 AM, "Michael E Caloroso" <mec.forumreader at gmail.com> wrote:
> 
> Clever indeed, looks like it took some inspiration from class G/H
> power amps.  Stability would be dependent on the input errors of the
> selected opamps.  Tempco would be a challenge.
> 
> MC
> 
>> On 11/15/14, Ove Ridé <nitro2k01 at gmail.com> wrote:
>>> On 15 November 2014 11:34, Paul Perry <pfperry at melbpc.org.au> wrote:
>>> I think this link shows how to overdrive the 741 output stages to get the
>>> square function and so on.
>>> http://2005.iccas.org/submission/paper/upload/2multiplier.pdf
>> 
>> No, what it actually seems to be doing is abusing the supply pins of
>> two of the chips. They are not connected directly to V+ and V-.
>> Instead, V+ and V- are treated as terminals connected to a current
>> source, and because of how the transistors are laid out inside, it all
>> works out. Very clever indeed! I need to build one now. This design
>> can likely be expanded to be used as a VCF as well.
>> 
>> --
>> /Ove
>> 
>> Blog: <http://blog.gg8.se/>
>> 
>> "Here is Evergreen City. Evergreen is the color of green forever."
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