CA3080 biasing

I just built a circuit:

https://www.electro-tech-online.com/custompdfs/2011/12/Syntom-2.pdf

and it works really nice after a lot of reworking

I was wondering though why the designer biased pin 4 of the CA3080 at 1.6v instead of ground as per the datasheet?

Neil.

Neil Groves said:

I just built a circuit:

https://www.electro-tech-online.com/custompdfs/2011/12/Syntom-2.pdf

and it works really nice after a lot of reworking

I was wondering though why the designer biased pin 4 of the CA3080 at 1.6v instead of ground as per the datasheet?

Neil.

Click to expand...

hi Neil,
Do you mean pin #5, the biassing pin.???
Its a split 9V supply, so with the 1k8 and 8k2 divider connected across 4.5V, you have approx +0.8V on pin 5.

This voltage is in line with datasheet of ~+0.7V for linear operation , rather than when used as Gating.

Its an awful drawing to read.

No Eric, i am refering to pin4, the data sheet says this is ground, they have it biased at 1.6V via the 8K2 and the 1K8....the circuit works fine, i am just curious

Neil.

Neil Groves said:

No Eric, i am refering to pin4, the data sheet says this is ground, they have it biased at 1.6V via the 8K2 and the 1K8....the circuit works fine, i am just curious

Neil.

Click to expand...

hi Neil,
Have drawn the circuit as shown in the designers document, using LTspice, so that I could run a simulation in order to find out why the divider is on the CA3080 0v pin.

I get a better result when pin 4 is connected directly to 0V.??

It looks as though the designer has decided to lift the CA3080 0V pin to +0.8v in order to change the effect of the VCA control, why I don't know.?

Perhaps it sounds better, just a subjective modification.?

NOTE: All controls shown as fixed resistors.
E

Thanks Eric, that looks interesting and does appear to make a difference, i'm not going to mess with it though as it sounds fine to me.

thanks

Neil.