Questions tagged [negative-voltage]

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70 views

Bipolar transistors that only connect via base to emitter

I am trying to understand how to use this configuration of the LTC2992 power measure IC and the only part I am confused with so far is the two transistors which I have circled. What I know so far ...
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2answers
92 views

Negative Voltage Output From Capacitor

Circuit Link I am very confused about negative voltage in capacitor, it can even light a led as you can see in the circuit. My questions are; 1-Why capacitor gives ~-2 V in its negative terminal ...
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1answer
62 views

LM2776 gets damaged after some time

It is almost the reference design from the DS. The only differences are those quite large inductances I had to add to remove the noise. The neg voltage is used to power RR OPamps feeding the ADC the ...
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1answer
22 views

Inverting negative voltage back to positive with LM324

To be able to measure the value with an Arduino Nano I want to convert the negative rail voltage to positive. I tried to build a simple inverting amplifier with unity gain using LM324. The supply is +/...
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2answers
139 views

Negative Voltage creating Sinking Terminal

For powering a RS485 circuit, I am requiring a Negative Power Source. I was thinking to split a standard power source with 0V, +6V and +12V, using the +6V as ground with LM7805, and using some LM7805|...
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1answer
43 views

Connecting negative terminal of DC power supply to negative terminal of other DC supply

I'm wiring up an electrical box that has several sensors, relays and a PLC. The PLC and relays are powered with a 24Vdc power supply. The sensors, which provide an analog input to the PLC, are powered ...
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1answer
64 views

how to choose a dual power supply for rail to rail amplifier?

I need +15VDC and -15VDC dual supply for rail to rail supply of op-amp. I have found buck-boost inverters used for this task. I have a doubt whether the inductor in the buck-boost inverter circuit can ...
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2answers
73 views

Negative Voltage In Capacitor When + Side Is Connected To -

Hello, i just didn't understand that why we get negative voltage(-4.7V) from capacitor's negative pole when we apply 0V to capacitor's positive pole.As i figured out, this is used in transistor flip ...
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1answer
102 views

Logic gate on negative signals

I need a logic gate to check if A or B or C is negative voltage (referenced to the ground). It does not matter if the output is positive or negative logic (as long as it is in positive voltages) Does ...
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2answers
78 views

Finding the negative feedback loop in the amplifier circuit

Today I was learning about the negative feedback in the amplifier circuits and some quick ways of discovering whether a negative or a positive feedback exist in the circuit by finding a feedback loop ...
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2answers
99 views

Negative Voltage Converter

I need to generate a negative voltage of approximately -12V from a 12V power supply. I read about ICL7660A that performs supply voltage conversions from positive to negative for an input range of +1....
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0answers
33 views

adjustable voltage controlled current source with negative values

I have a MEMS mirror which can tilt based on the input current. The current can vary between -15mA to +15mA in order to change the angle of the mirror from -15 to +15 degree. Now, I need to have an ...
2
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3answers
386 views

Supply current of negative rail

I'm using an LTC1983ES6-5 to provide a negative rail for both a MAX4311 and a MAX4395. LTC1983 provides up to 100 mA, but I cannot find in the other datasheets how much current is required for the ...
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0answers
42 views

Why is my signal stronger in the positive than in the negative when i use 2n3819?

simulate this circuit – Schematic created using CircuitLab In the above circuit I have created a JFET amplifier for small signal purposes. When I run tests on the circuit, i get this weird ...
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4answers
74 views

24V DC to +5V and -5V

I need to convert 24V DC to +5V and -5V to power two op-amps (opa2134) and one ATtiny85 with minimal heat generated from the circuit. What voltage regulator would you recommend ? //Digis
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3answers
280 views

ICL7660 - Cannot provide stable negative voltage for audio amplifier

I built this audio amplifier mainly with UA741, ICL7660 etc. The VCC is 5 volt from USB. But I found that the -VCC is quite unstable and this caused noise from speaker, which can hear even when music ...
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3answers
135 views

Current sensing on negative 1.1kV DC rail

I searching for a way to do high side current sensing on a -1100V DC rail. My HV is generated from the hamamatsu C9619 High voltage power supply module and it powers the hamamatsu R647P ...
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3answers
235 views

Is there truely such a thing as a negative DC voltage (with reference to earth ground)?

I understand the concept of a negative voltage. Ground is a reference point and it's easy to get a negative voltage if your ground reference is above earth ground. Does a differential power supply ...
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3answers
302 views

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?...
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2answers
308 views

Negative Voltage Reference for Bipolar ADC

I am considering using ADS1258 - a bipolar ADC. It needs an external reference across REFP(+) and REFN(-). How do I generate precise -2.5V assuming I have +12V and -12V analog voltage rails? I can ...
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2answers
97 views

Polarity question

In a -48 volt DC power plant system how do you determine the polarity of 0v? trying to resolve an issue and not sure how to correctly identify
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3answers
1k views

Generating a Negative Voltage

In general, there are many ways for DC-DC conversion: SMPS, charge pump, linear regulators, zenner diodes, even resistive dividers. But lets say I want to create 2 voltage rails, +Vcc and -Vcc. I can ...
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2answers
131 views

How to obtain negative and positive voltage (±16V) for LM324N

I'm working with the LM324N op-amp. My project requires dual supply, ±16V. How can I produce negative and positive supply from a single supply source? Some project have been using ICL7760 to obtain -...
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4answers
1k views

Are there any single supply OP amps with negative supply voltage?

I learned that basically the only difference between a "single supply" OP amp and a dual supply one is that the former can drive much closer to the negative supply rail. Furthermore if I understand ...
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1answer
156 views

Use Raspberry Pi to power a low noise inverting amplifier with negative voltage input

I am looking to use a Raspberry Pi to power and read the current from a current-to-voltage converter. I am currently using two batteries to power the operational amplifier, as shown in the schematic ...
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3answers
110 views

LM2664 noise in the OPAMPS output signal. How to remove

I have 4 opamps powered from the LM2664. Two of them (1MHZ 1.6V R-R) are preparing the offset voltage for the pair of the OPA4141 which actually provide the signal for the ADC It works as expected ...
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1answer
695 views

Switching positive and negative voltage

I struggle to understand how can you switch positive or negative supply from a battery. Firstly, what is a positive voltage and negative voltage? I read many posts stating it all depends on your ...
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6answers
1k views

What is the most painless way to get a high current negative voltage power supply from a positive?

I'm designing an audio DSP and DAC board, and in the analog section, I'm using opamps that take in differential audio signal and turn it into single ended output. Because the signals are AC, they ...
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3answers
1k views

Power Supply negative voltage as ground and ground

I have a PC PSU and can get GND +5V +12V +3.3V and -3.3V -5V -12V out of it. I need to power a device that needs more than 12V. Am I able to take the -5V as GND and connect +12V to VCC and still use ...
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1answer
91 views

Inverting regulators and sinking current

I have a circuit to drive a simple resistive load, and it works quite well. On the high side is 2.5V from a regulator, and the low side is 0V (taken as reference to a battery's negative terminal which ...
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1answer
64 views

maximum emitter base reverse voltage limiting when driving with op amp?

This is part of a larger circuit, but problem area is shown below. In simulations (of the larger actual circuit not shown), the base voltage of Q1 drops to about -6.35V. Can this damage Q1 (2N3904)? ...
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0answers
235 views

Transistor logic to drive h-bridge with negative voltage source

Shown below is a H-Bridge circuit I have used to drive the cathode of a VFD display with a source voltage of +2.4V with a +3.3V digital logic level. I have decided to switch the cathode source ...
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3answers
1k views

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 +...
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3answers
5k views

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 ...
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1answer
107 views

MC34063ADR overheats and burns

I am trying to get -13.5V from mc34063. On the first design, I used 8DIP package MDR34063AP and no problem getting -13.5V. On the second design changed the package to 8-soic and used S1B-13F (100V ...
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1answer
197 views

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?
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1answer
402 views

Polarised capacitor - negative voltage?

I designed a circuit that is similar to the circuit on the picture below. The main difference in my design is that I am using a 3V battery and more LEDs. I am using UNPOLARISED capacitors because I ...
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2answers
440 views

Single ended ADC negative voltage protection

How to protect ADC input against the negative voltage?
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1answer
229 views

Regulating Negative Voltage

Can the TL783 be used to regulate negative voltage by connecting the output to my system ground and using the regulator ground as my negative voltage source? I couldn't find anything in the datasheet ...
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0answers
53 views

Apply positive and negative voltage to component using single power supply [duplicate]

I have an electromagnet and a 12V power supply. I would like to apply +12V to the electromagnet at some times and -12V at other times. My current thought is to use four transistors (two NPN, two PNP) ...
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1answer
829 views

Truth Table for 3-into-8 decoder with N.A. inputs, P.A outputs and enable

I'm working on an assignment where I need to draw a block diagram and the gate-level circuit of a 3-into-8 decoder with negative active inputs, a positive active enable and positive active outputs. ...
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2answers
128 views

Detecting ground on GPIO and protect from positive voltage

I need to sense a logic low on the GPIO. The input will come from external resources (By end user) so I need to protect the circuit as well from high positive voltage. Generally the circuit will be ...
0
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1answer
378 views

Using Switching Regulators to Make Split Supply

I am trying to use two switch-mode regulators to create a split supply, where the first one regulates the positive voltage as per the application schematic in the datasheet and the second one works ...
2
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1answer
451 views

Op Amp Power Supply Consideration

When choosing a split supply for an op-amp circuit, how do I determine my power supply requirements? For a single supply, this is easily determined by finding the required current - but how is power ...
4
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2answers
964 views

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 ...
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1answer
1k views

Negative Voltage Supply Indicator Led

I am intending to make an indicator led circuit which shows the negative 9 V supply is coming to the circuit and led becomes on, but if there is zero volts, the led will be off. I have done this ...
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2answers
87 views

Comparing voltages

I'm trying to design a system that compares two DC voltages and if they're "close" one to the other, enables an output that controls a relay. Essentialy, given 2 voltages \$V_a\$ and \$V_b\$, I want: ...
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2answers
100 views

Negative Supply

I am thinking to test an IC which have +9V and -9V supplies. To obtain a -9V, i intend to reverse connect a +9V battery. What can be negative effects, if there is? Thank you so much.
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2answers
2k views

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?
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2answers
773 views

Voltage Generator with Full Wave Rectifier

I have simulated a circuit which gives +12V and -12VDC output. I am planning to obtain input signals from a transformer. I have some questions related to it, if you share your ideas i will be very ...