# generate 24V DC and -24V DC signals from a single 24V generator using inverting amplifier ??

#### Oussama Zaidi

Joined Mar 1, 2016
53
Hi everybody
Can I use an inverting amplifier to generate both 24V DC and -24V DC from an inverting amplifier without losing any of the 2 voltages, I tried different montages but always I found that I can keep only one voltage if I generate -24V by using the inverting amplifier then the voltage of the generator drop down and I need both of them, can any one help me please, thank you.

#### Roderick Young

Joined Feb 22, 2015
408
What is called an inverting amplifier can typically only output voltages that are supplied to it. So if you supply the amplifier with +24V and 0V (ground), then your output signal is generally between +24V and 0V.

How much power is required? If very little, a circuit called a charge pump might be enough. Just an integrated circuit and some capacitors. If more power is required, what is called an Inverting DC-DC converter might be enough. What did you want to power from the dual 24V supplies?

• Oussama Zaidi

#### Oussama Zaidi

Joined Mar 1, 2016
53
What is called an inverting amplifier can typically only output voltages that are supplied to it. So if you supply the amplifier with +24V and 0V (ground), then your output signal is generally between +24V and 0V.

How much power is required? If very little, a circuit called a charge pump might be enough. Just an integrated circuit and some capacitors. If more power is required, what is called an Inverting DC-DC converter might be enough. What did you want to power from the dual 24V supplies?
Thank you Roderick for your response, I need the positive and negative voltages to supply some amplifiers, I tried to use some DC_DC converters like LT8330, I simulate it in LTSPICE but it didn't gave me a good result also I can't found it in any other PCB design program eagle,ISIS and Altium designer, it is became really hard for me to found a circuit that converts +24V to -24V or even -20V doesn't matter just I need a high voltage less than -20V.

#### crutschow

Joined Mar 14, 2008
23,487

#### Oussama Zaidi

Joined Mar 1, 2016
53
How much current?
The current depends on what charge I will put on the output of the regulator no ?? I need +24V and -24V to supply 16 amplifiers, I don't know honestly how much current does that mean.

#### ScottWang

Joined Aug 23, 2012
6,829
Assuming that the conversion efficiency = 80%, Wout = Win * Eff = Win * 80%,
Win = Wout / 80%
= (48V * 16A) / 80%
= 768W / 80%
= 960 Watts
So the input Power needs 960 Watts

Ii = Win / Vi
= 960 W/ 24V
= 40 A
So the input current needs 40 A

Assuming that the conversion efficiency = 90%, Wout = Win * Eff = Win * 90%,
Win = Wout / 90%
= (48V * 16A) / 90%
= 768W / 90%
= 853.3 Watts
So the input Power needs 853.3 Watts

Ii = Win / Vi
= 853.3 W/ 24V
= 35.6 A
So the input current needs 35.6 A

How much output current of generator?

#### crutschow

Joined Mar 14, 2008
23,487
The current depends on what charge I will put on the output of the regulator no ?? I need +24V and -24V to supply 16 amplifiers, I don't know honestly how much current does that mean.
I don't know what you mean by the "charge" on the output of the regulator. Regulators supply voltage and current.
The amount of current depends upon what the amplifiers need.
What is the power rating of the amplifiers?

#### nigelwright7557

Joined May 10, 2008
532
Sounds like you need SMPS or a linear power supply.

#### Oussama Zaidi

Joined Mar 1, 2016
53
I don't know what you mean by the "charge" on the output of the regulator. Regulators supply voltage and current.
The amount of current depends upon what the amplifiers need.
What is the power rating of the amplifiers?
charge that is mean load in french I am sorry, the load here are the amplifiers, I have an external generator that gives me 24V stabilized this generator is the only supply for the circuit, I have 8 amplifiers of LT1014 each one consume 0.5mA maximum of supply current so I need only 5mA of current max so if the regulator can deliver much more what is the problem?? it will deliver only what the amplifiers needs no ??

#### Oussama Zaidi

Joined Mar 1, 2016
53
Assuming that the conversion efficiency = 80%, Wout = Win * Eff = Win * 80%,
Win = Wout / 80%
= (48V * 16A) / 80%
= 768W / 80%
= 960 Watts
So the input Power needs 960 Watts

Ii = Win / Vi
= 960 W/ 24V
= 40 A
So the input current needs 40 A

Assuming that the conversion efficiency = 90%, Wout = Win * Eff = Win * 90%,
Win = Wout / 90%
= (48V * 16A) / 90%
= 768W / 90%
= 853.3 Watts
So the input Power needs 853.3 Watts

Ii = Win / Vi
= 853.3 W/ 24V
= 35.6 A
So the input current needs 35.6 A

How much output current of generator?
what 16A ?

#### ScottWang

Joined Aug 23, 2012
6,829
what 16A ?
You saying that you need the power to supply 16 amplifiers, I'm not sure how much ampere you need, so I assuming that each amplifier needs 1A then you will need 16 A.

#### crutschow

Joined Mar 14, 2008
23,487
The LT1014 can't work on ±24V.
The absolute maximum supply voltages for that amp is ±22V.

#### Oussama Zaidi

Joined Mar 1, 2016
53
@crutschow Yes I know I don't need exactly -24V just less than -20V and even if I have -24V it is not a problem I can use a voltage divider or other staff to fix it just now I need a circuit that gives me a negative voltage from 24V DC.

#### crutschow

Joined Mar 14, 2008
23,487
Why do you need both plus and minus supply voltages? That op amp will operate with a single supply down to 0V.
What is the signal you are trying to amplify?

#### Oussama Zaidi

Joined Mar 1, 2016
53
Why do you need both plus and minus supply voltages? That op amp will operate with a single supply down to 0V.
What is the signal you are trying to amplify?
@crutschow I need to generate a signal between 20V and -20V from a signal between 0 to 3.3V that is why I need both positive and negative supply voltages.

#### ScottWang

Joined Aug 23, 2012
6,829
Assuming that the conversion efficiency = 80%, Wout = Win * Eff = Win * 80%,
If Each op amp drawing 50 mA, then 16 pcs will be drawing Iout = 50 mA * 16 = 800 mA = 0.8A
Win = Wout / 80%
= (48V * 0.8 A) / 80%
= 38.4W / 80%
= 48 Watts
So the input Power needs 48 Watts

Ii = Win / Vi
= 48 W/ 24 V
= 2 A
So the input current needs 2 A

Assuming that the conversion efficiency = 90%, Wout = Win * Eff = Win * 90%,
If Each op amp drawing 50 mA, then 16 pcs will be drawing Iout = 50 mA * 16 = 800 mA = 0.8A
Win = Wout / 90%
= (48V * 0.8 A) / 90%
= 38.4W / 90%
= 42.7 Watts
So the input Power needs 42.7 Watts

Ii = Win / Vi
= 42.7 W/ 24 V
= 1.78 A
So the input current needs 1.78 A

#### Oussama Zaidi

Joined Mar 1, 2016
53
@crutschow @ScottWang I found the LTC3260 it is a switching regulator which gives me -24V, -12V and +12V it is perfect for me because I need lower voltages too but I can't found it in any PCB design program that I know, do you know a program where I can realise a layout with this part, or how to add it to Altium designer or Eagle libraries ? I have already Linear Technology library in both of programmes but this part doesn't exist :/.

#### Oussama Zaidi

Joined Mar 1, 2016
53
@ScottWang No, it is 0.5mA for each amplifier, not 50mA, also i can't understand what do you mean about input current if it is the input of the regulator i don't have any problem because it is connected to a power supply that gives me any current i need, it is a generator connected to the grid.

#### crutschow

Joined Mar 14, 2008
23,487
@crutschow @ScottWang I found the LTC3260 it is a switching regulator which gives me -24V, -12V and +12V it is perfect for me because I need lower voltages too but I can't found it in any PCB design program that I know, do you know a program where I can realise a layout with this part, or how to add it to Altium designer or Eagle libraries ? .............
You likely need to generate your own part.
I don't know the details but I'm sure the help files will tell you how add parts to either Altium or Eagle.
Find the package you want to use and add the pin designations, then save it as LTC3260.