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CONVERT from 15-0-15v to 9v

polyal

Sep 8, 2011
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i have a mains powered 1khz test tone oscillator i need to
make portable
i need to convert it from 15-0-15 split rail to 9v ( battery )
this circuit generated 10v p/p
what modifications do i need to do to get about a 2v p/p sine wave
cheers reg1khz oscillator.png
 

Alec_t

Jul 7, 2015
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This should do what you want :-
1665142133743.png
Note the new split supply with a virtual ground (4.5V), the addition of a 10k pot to give you an adjustable output amplitude, and that the non-inverting inputs of the op-amps connect to the virtual ground. The other component values are unchanged.
 

polyal

Sep 8, 2011
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thanks . . i will try that
regards
reg

ps is the pot grounded at the battery negative or should it be at
the virtual earth ? ie is the signal relative to the batt negative
 
Last edited:

Alec_t

Jul 7, 2015
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The pot can be grounded at either, since the output is capacitor-coupled. What will the pot output be feeding?
 

polyal

Sep 8, 2011
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it works spot on:)with either ground or -ve
i'm getting a 1v p/p sine wave ♪♪ ( at the op amp o/p )
is there anyway i can squeeze another 1volt gain out of it
it will be used for signal tracing through audio gear typically
at line level ( mixers etc )
the circuit is from a vintage soundcraft delta mixer
thanks
reg
 

Alec_t

Jul 7, 2015
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i'm getting a 1v p/p sine wave ♪♪ ( at the op amp o/p )
Which op-amp? (Either should give at least 5V peak-to-peak output if all component values are as shown in the circuit I posted.)
Do you have both non-inverting inputs (pins 3 and 5) connected to the virtual earth?
Are you sure the battery is putting out 9V under load (~9mA or more)?
What load do you have on the pot wiper?
What is the virtual earth voltage relative to battery negative?
 
Last edited:

polyal

Sep 8, 2011
21
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thanks for the reply
it turned out to be a build fault due to using recycled
strip board with cut track ( R10 was not connected to virtual earth )
it has now been rectified and giving a healthy 4v p/p sine wave
thanks for your help . . well chuffed
♪reg♪
 
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