Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [negative-voltage]

136 questions
19
votes
3 answers

Difference between 0-18V and -9V - +9V

What is the principle of the difference between a supply which provides 0-18V and +9V and -9V? If I am using a circuit which takes a +/-9V power supply, and instead start powering it with 2 9v batteries, is there a fundamental difference in the…
TCassa
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11
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5 answers

Is it OK to create a negative rail just by dividing voltage with resistors?

I want to build some circuits to learn about op-amps, and so I would like to set up a negative rail. Are there any problems in creating a negative rail by using an 18 V bench supply and then simply dividing the voltage using, say, two 10 MΩ…
JohnnieL
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7
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2 answers

In an ATX power supply, how is the -12V supply made?

I was looking at a pin out for a 20 pin ATX power supply and noticed a -12V pin. I am now wondering; is this just a ground? If not, how does the PSU make a -12V supply rail?
McMuffinDK
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6
votes
5 answers

How do you calculate negative and postive voltages in a grounded circuit?

This may be a vintage question, I'm not sure. I am self-studying electronics using some old books and came upon the problem below from "Basic Electronics" by RCA Institutes, 1965. The book is fantastic, but some of the terminology and tech is…
decuser
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6
votes
5 answers

How to make a simple negative power supply

I want to experiment with amplifiers but I need a negative power voltage source. I looked for some circuits but as far as I found they either are not simple & reliable or require an IC. Is there any simple way to get negative power supply without…
Mordecai
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6
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3 answers

How to turn a 0 to 5V square wave pulse into a -500mV to +500mV square pulse using just passive components?

Let me start out saying I'm not trying to build anything specific or useful here, just trying to learn the behavior of circuits. Is it possible to turn a 0 to 5V square wave pulse into a -500mV to +500mV pulse using just passive components and where…
acker9
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4
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3 answers

How to generate -5 V from +5 V and GND?

I have an Arduino providing +5 V and GND. I have a component that requires +5 V, common GND, and -5 V connections. Is it possible to generate -5 V? If not, what input voltage do I need? I am driving a bias controller for an RF switch PIN diode. I…
Power_tile
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4
votes
0 answers

Switching load with changing polarity

From a bespoke board I'm receiving 18vdc that I need to switch. This 18vdc will usually be +18vdc but at times can be -18vdc. The load is .35A. The polarity is being changed via a H-Bridge and unfortunately it's not possible to do the switching…
chip
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4
votes
3 answers

Do an Op-amps supply pins need to have the exact same nominal voltage?

By power supply unit should ideally output +12 and -12V, however the readings are closer to 12.2V and -11.8V. Is this likely to cause a problem, even though I only need an output range of 10V to -10V?
19172281
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4
votes
1 answer

LM2664 can I use the ceramic capacitors instead of the electrolytic ones?

I need the negative voltage for my OPAMP and I use the LM2664 inverter. I have a very limited space available on my PCB. Is it OK to replace the electrolytic capacitors with the ceramic ones?
0___________
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4
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2 answers

Where to ground low pass filter before dual supply operated op-amp?

The circuit below shows my setup. The resistor and capacitor act as passive low pass filter. In my setup the C1 is grounded to GND (0 V) but the op-amp operated with dual supply (+-5V). My question is this, do I need to ground the C1 to -5V for…
user30878
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3
votes
4 answers

How can I supply −5 V to an op-amp?

This is the circuit that I intend to implement on a breadboard. I only have an ESP32 microcontroller, so I can supply the +5 V, but I have no idea how to supply the −5 V. If I change Vee to 0 V (GND on the ESP32), the circuit will not work as…
Scipio
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3
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2 answers

Does 7905 needs minimum load current?

In the 7905 negative voltage regulator datasheet, it didn't mention that it needs a minimum load current to operate. The 7905 that I have is outputting -7 V but adding a ~2 mA load causes the voltage to drop to nominal voltage -5 V. Input is -15…
ElectronSurf
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3
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3 answers

Logic Level Converter for Negative Voltages

Here is logic level converter mostly used for converting signals between 3.3V and 5V. (Other positive levels such as 1.8V are also possible). What if I want to convert from 3.3V to -5V logic (negative!)? It doesn't have to be bi-directional. Could…
tarik
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3
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1 answer

Generating negative voltage rail using P7805 DC-DC converter

I need to create a negative voltage rail (from positive supply rail), say -5V to keep a P-MOS transistor in ON-state even when the voltage on its [S] source is 0V. So I found this schematic in an answer of another question here, but does this…
velizarw
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