negative supply

[t.man]

how can one make a negative voltage supply? would interchanging the wires of, say a 12V adapater, suffice?

 

[ericgibbs]

how can one make a negative voltage supply? would interchanging the wires of, say a 12V adapater, suffice?

hi t,

Buy a mains 12V dc plug adaptor and you can use it either has a +12V or -12V supply, connect the +V lead to your circuit 0V/common and the other lead is the -V12.

 

[t.man]

hi t,

Buy a mains 12V dc plug adaptor and you can use it either has a +12V or -12V supply, connect the +V lead to your circuit 0V/common and the other lead is the -V12.

i dont know if i get you. are u saying i should connect ,what i normally use as +12V lead, to 0V/GND . because when i use multimeter i can see when i interchange leads i measure negative voltage.

 

[ericgibbs]

i dont know if i get you. are u saying i should connect ,what i normally use as +12V lead, to 0V/GND . because when i use multimeter i can see when i interchange leads i measure negative voltage.

If you use separate 12Vdc psu adaptor, connect the +12V lead to 0V ground and the other lead is -12V.

Think of it like a 12V battery, you can connect those either way around to give a +V or -V with respect to 0V.

OK.?

 

[t.man]

If you use separate 12Vdc psu adaptor, connect the +12V lead to 0V ground and the other lead is -12V.

Think of it like a 12V battery, you can connect those either way around to give a +V or -V with respect to 0V.

OK.?

I can not use the same psu adapter to provide both +V and -V?

 

[karuppiahsaravana]

Hi,

You Can'not use same adaptor for both + & - 12V. If You want +12v & - 12 v in single Adaptor then go for 24 volt Adaptor (transformer) and use regulator 7812 & 7912 with filter 1000mfd Capacitor.

 

[ericgibbs]

I can not use the same psu adapter to provide both +V and -V?

hi t,
As already pointed out, its not possible to use a single 12Vdc adaptor for both the +12V and -12Vdc.

Exactly what are you trying to do with these supplies.?

 

[t.man]

Exactly what are you trying to do with these supplies.?

it is for this amplifier circuit. it uses LF442-CN. so i can see it'll require +15V and -15V. am i right?

if yes, how can i supply these voltages?

 

[ericgibbs]

it is for this amplifier circuit. it uses LF442-CN. so i can see it'll require +15V and -15V. am i right?

if yes, how can i supply these voltages?

hi,

Are you amplifying ac or dc signals, and ver what range of input/output voltages.?

Do you have a circuit diagram.?

 

[t.man]

hi,

Are you amplifying ac or dc signals, and ver what range of input/output voltages.?

Do you have a circuit diagram.?

i think its dc. im not sure of input signals but output runs from 0 to about 2.5V or something like that

 

[ericgibbs]

i think its dc. im not sure of input signals but output runs from 0 to about 2.5V or something like that

hi t,
The input pin3 is grounded, but you have a 10K going to 15V on pin3.? also a 10uF.?

You could consider using a 7660 -Voltage generator ic, running from the +V rail to give a negative voltage.
There are more modern/better devices than the 7660, but it will give you an idea.

If an output voltage of close to 0V to say +2.5Vdc is OK, it would be possible to use a OPA that will work from a single supply.

EDIT:
You could build one of these 555's

 

[t.man]

hi t,
The input pin3 is grounded, but you have a 10K going to 15V on pin3.? also a 10uF.?

You could consider using a 7660 -Voltage generator ic, running from the +V rail to give a negative voltage.
There are more modern/better devices than the 7660, but it will give you an idea.

If an output voltage of close to 0V to say +2.5Vdc is OK, it would be possible to use a OPA that will work from a single supply.

EDIT:
You could build one of these 555's

use this as -V supply?

 

[ericgibbs]

use this as -V supply?

If you build that 555 -Vgenerator, you should a few volts negative to power the OPA.

 

[Hero999]

You could buy an adaptor with 12VAC output and use a diode voltage doubler to get a positive and negative supply.

 

[t.man]

hi t,
The input pin3 is grounded, but you have a 10K going to 15V on pin3.? also a 10uF.?

You could consider using a 7660 -Voltage generator ic, running from the +V rail to give a negative voltage.
There are more modern/better devices than the 7660, but it will give you an idea.

If an output voltage of close to 0V to say +2.5Vdc is OK, it would be possible to use a OPA that will work from a single supply.

EDIT:
You could build one of these 555's

which 555? LM or NE?

 

[ericgibbs]

which 555? LM or NE?

hi t,
I would use a TTL version, IIRC they can output about 200mA.

EDIT: added a data extract.

 

[t.man]

hi t,
I would use a TTL version, IIRC they can output about 200mA.

EDIT: added a data extract.

so i only use my +12V supply as input to VCC and ground and i get -VCC as output to supply my circuit?

 

[ericgibbs]

so i only use my +12V supply as input to VCC and ground and i get -VCC as output to supply my circuit?

hi,
Thats the way its usually done.

 

[t.man]

hi,
Thats the way its usually done.

hi, i want to check the items at the store, what values are the caps? i.e is it 220uF and 0.05uF?

 

[ericgibbs]

hi, i want to check the items at the store, what values are the caps? i.e is it 220uF and 0.05uF?

hi,
They are 220µF at 16Vwkg[min] Electrolytic and a 0.05µF ceramic, a 0.047µF would be OK.

Any of the 1N400x diodes will be OK.