THAT1646 on a single supply?

[3nity]

I have + 24V and i need to power a THAT1646 ....what would be the best way?? to get the 1646 to work?
At some point i have +18V and tought about using this on a single supply...

Jorge Aristondo.

 

[Svart]

You have to bias all inputs to half rail that's all.

 

[3nity]

could the biassing be made from the -V??

 

[Andy Peters]

could the biassing be made from the -V??

??? In single-supply operation, V- (VEE) is grounded.

- a

 

[hobiesound]

in a single supply circuit you make the bias voltage from a voltage divider in between V+ and ground.

Even a guitar pedal brewing pot head like me knows that 

good luck,

Thomas

 

[3nity]

i know`all that....but i think i saw a design based on a single negative supply...??? ???

 

[skipwave]

You've built BabyAnimal mic preamps right? Look at that schematic. It shows the voltage divider and the 1/2 rail bias fed to both inputs of the opamp.

 

[3nity]

thanks in reality just wanted to make sure that the 1646 would work on a single supply!
Thanks Skip thats a clear example indeed.

 

[3nity]

just wanted to wake this thread by post this circuit i found by Wayne.
Thanks.

 

[Svart]

Not sure I understand why Wayne used an opamp as an active buffer for that biasing on pin 3 of the THAT ic.  I suppose he wanted a low impedance source but I think the input impedance is low enough on pin 3 of the THAT IC that a simple decoupled resistor divider would suffice.  Use around 4k7 up to 10k instead of the 100k resistors, tie that to pin 3 of the THAT IC (get rid of U2A) and remove R2/C4.

The other possible solution is to connect the part to the 24v rail and ground but AC couple all I/O through capacitors.  C1, C2, C3 are already coupled.  Try removing everything connected to pin 3 of the THAT IC except R2/C4 and make C4 something large like 100uf.  The part should self bias around half rail (12V) as long as there is no other DC connection.  This is, however, guessing since I don't know the part at all but I've done it with other diff amps with no problems.

 

[JohnRoberts]

From a quick glance at the part http://www.thatcorp.com/datashts/1600data.pdf there are internal feedback path resistors looking for a low impedance ground at that "ground" input. Clearly designed for bipolar operation.

JR

 

[Svart]

Yes you are right.  Keep the opamp.