An electronic component that sources current - if it sinks current it is called a current sink but both devices (sinks and sources) can be called sources. An IDEAL current source will supply current , maintain high voltage compliance (i.e. adapt it's output voltage to match the network it is ...

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2answers
83 views

Zener Diode Current Source

How would I make a Zener diode current source? Something like this? I don't know how to figure out what resistors/transistors/diodes I need. I guess what I'm asking is, how do I calculate what ...
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1answer
73 views

How to eliminate early effect in constant current source

When designing an differential amplifier it is important to have a precise constant current source (which I will abbreviate with CCS). It helps to keep out signal injections from the supply rails. A ...
0
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3answers
91 views

Current flow through a battery

So this might be a stupid question and I really should know the answer to it but I am having difficulties with a circuit I have made to drain a battery. The basic idea of this circuit is that I have ...
0
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1answer
29 views

Current Injection Via Jumper Design Help

I am currently designing a circuit that uses a 5V 2A power brick. The circuit requires a current source and I have seen good efficiency with Ohm's Law. The current is variable through a 2k ...
2
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2answers
84 views

Sourcing current with sink LED driver

I'm using an existing keypad with 8 LEDs that source power. I was hoping to use and LED driver of sorts, but all of the ones I find only refer to sinking power. Is it possible to use these drivers to ...
2
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3answers
86 views

How do I keep my constant current source constant?

So I am trying to created a current source that will be used to drain a battery at specific time intervals for a specified duration. simulate this circuit – Schematic created using ...
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1answer
61 views

Combine two signals of different frequencies in a test setup

I have a device that is powered from a current source. The current source supplies 10A at 60Hz - the magnitude is roughly 5-10VPP. I would like to inject another signal on top of that to simulate ...
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2answers
86 views

Parameters for voltage-controlled current source

I'm trying to implement the following circuit in a project: VCC coming in is 18v. The op-amp is supplied with 3.3v. There is a waveform voltage input from 0-2 v that can oscillate at up to 100hz, ...
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3answers
112 views

how to create a high current source?

I'm looking to observe magnetizing offsets of various current sensors. The idea is that when you pass a high current pulse (close to the rating of the device) through a current sensor and then return ...
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3answers
105 views

Current source for milliohm loads?

I've been working on a model maglev train as my Grand Hobby Project; something around the H0 scale. The initial idea was to use the Inductrack mechanism to keep it simple. To summarize, a Halbach ...
2
votes
1answer
97 views

Current source improves linearity on collector BJT

I'm learning about analog electronics. I'm looking into amplification stages at the moment. Question 1: Single BJT C-E Amplifier. Usually you put a resistor between collector and V++, so as \$I_b\$ ...
1
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2answers
69 views

Current controller circuit to drive solenoid bank

I am working on building a current controller circuit used to drive 8 solenoids (for those interested, the solenoids produce magnetic fields for use in a Zeeman Slower). My problem is that there is ...
12
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3answers
1k views

Do constant current batteries exist?

Do constant current batteries exist? If not, why not? Else, why are they not very common in the market? I am not talking about an ideal current source. But it should be a constant current source for ...
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2answers
43 views

Total current in two circuits - two methods

I have two norton's theorem questions and I am confused about the two solutions. In the first one below, the current can be found by simply subtracting one current from another. (I believe this is ...
3
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2answers
107 views

Standard current and discharge current

I've been looking into batterie's datasheets and don't understard what 2 of the specifications mean: continuous standard current and maximum continuous discharge current. Could someone explain this to ...
1
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2answers
82 views

Current source - Achieving a defined settling time with variable load resistance

I'm trying to build a voltage-controlled current source which is supposed to work with a wide range of load resistances. Currently the plan is to use an NPN transisitor as voltage follower to do the ...
1
vote
1answer
64 views

Nodal analysis independent and dependent voltage source and current source

After spending quite a few hours I am stumped with this problem while trying to solve for Vo, which is supposed to 0.5V and this was confirmed through PSpice. I have no idea what I am doing wrong or ...
3
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2answers
220 views

Superposition principle: Dependent sources treated as independent sources

Since I began studying, I was taught that when analysing a circuit using multiple sources, independent sources could be turned off, meaning that I could transform a voltage source into a short, and a ...
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1answer
30 views

Find four current mesh

I have to find the 4 current mesh in this circuit V1= 12V R1= 1/12Ω R2= 1Ω R3= 1/3Ω I1= 6A R4= 1/3Ω R5= 1/2Ω R6= 1/13Ω I2= 6A I tried a source transformation and got this I3= 144V R1-2= ...
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1answer
103 views

Current Controlled Output Using PWM

I am looking to control a proportional valve with a PWM signal that will correlate into exact current amounts (for example a 25% duty cycle will output 200mA, and a 90% duty cycle will produce let's ...
1
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1answer
34 views

Cadence, BSIM3V3, and the Body Effect

I am trying to meet the compliance/min output voltage of a wide swing current mirror so the output current (10uA) is within .1% or +/- .01uA. I am using Cadence and ami06 nFET's to do so. I am always ...
2
votes
1answer
32 views

Special Source Transformations

I'm not sure if this was asked already, but I could not find it when I searched. We're learning about source transformations, and while reading my textbook I came across this: and in the following ...
0
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1answer
50 views

What Formality Am I Using To Isolate This Portion Of The Circuit?

If I have this circuit in which the switch opens at t = 0 (after being closed for an infinite time, making the circuit steady state), for which I'm trying to find the voltage across R2 as a function ...
1
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6answers
333 views

Is there any physical device called current source?

I have seen both current source and voltage source in many electrical circuits (in paper). When it comes real hardware battery can be considered as a voltage source. Then what is a current source ? ...
0
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1answer
44 views

Which options exist for switching the polarity of an output with low leakage?

In my application, I want to switch the polarity of an output which supplies a controlled current up to 50mA (accuracy 100uA + 1%) at up to 36V. The current sensor is on the low side of the output. ...
0
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2answers
84 views

Switching current source ~1 μA — how to switch off quickly?

I would like to have a precision current source ~1 μA loaded by a resistor ~100k and a voltage source. Also I would like to switch on and off the current. The problem is that when the transistor ...
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1answer
61 views

How do you find the equivalent voltage of the current source in this circuit? [duplicate]

The circuit is shown at this schematic. How do I find the equivalent voltage of the current source by simplifying the circuit?
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2answers
106 views

Equivalent circuit?

Can I simplify this circuit to just one resistor? How can I find the equivalent voltage of the current source in this circuit?
2
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1answer
144 views

Understanding 74LVC245 datasheet and current source/sink

I'm using a SN74LVC245A (datasheet) to shift 5V TTL down to 3.3V so I can read the signals with a Raspberry Pi. However I am getting really weird results (a 60Hz input signal is picked up by the Pi ...
3
votes
3answers
248 views

Maintaining a constant current with varying loads

I've designed a constant current source using a current mirror, we need an output of about 50mA. The problem is that we build it and heat has become a problem.The transistors and the R_load are both ...
2
votes
2answers
135 views

Howland Current Pump VS Wilson Current Mirror

I am interested on knowing what would be a better solution to create a current source for low current applications (below 20mA), an opamp based current source such as a Howland current pump (link to ...
7
votes
4answers
1k views

Choosing resistor values for non-inverting amplifier and why?

The gain here is A = -Rf/Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why? I know that you could have infinite number of combinations for these ...
1
vote
1answer
107 views

How can I model a variable current sink in spice?

For a project I am working on (related question here) I need to model a nonideal variable current sink in spice. Simply reversing the orientation of a current source or inverting its value is not ...
1
vote
1answer
54 views

How do I increase (multiply) the value of a current sink?

I have been shown an IC that is a current sink PWM dimmable LED regulator. It happens to be a WS2811. While this works well for low drive currents (up to about 20mA), I was approached with the idea of ...
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3answers
496 views

Constant Current Source circuit improvisation

simulate this circuit – Schematic created using CircuitLab I was wondering whether I could use this circuit as a constant current source provided my load circuit impedance was less than ...
2
votes
3answers
216 views

How to make a constant current source

I don't understand current sources! Batteries are voltage sources, but how does one actually implement a current source? I was looking at current mirrors to see how they work, and I understand the ...
0
votes
1answer
58 views

Bipolar Transistor PTAT Cell and setup

I am in a measurement systems class at school, and we have a project to design a measurement system. I was reading my text book when a diagram caught my fancy, and I thought I would try to build it. ...
1
vote
1answer
115 views

Can't figure out voltage-controlled current sources

I'm trying to teach myself how to wire circuits, but I don't know if I got the correct answer for this? Where is a good place for me to learn the order of operations for solving circuits? Thanks.
0
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0answers
31 views

Split common resistance to input and output port

I have a circuit like this. simulate this circuit – Schematic created using CircuitLab I need to represent R1 in both input and output side so that R1 can be removed from the circuit. I ...
0
votes
3answers
143 views

op-amp replacement

I am trying to built this current source, but he LM107 seems to be discontinued, what opamp could I replace it with? I dont know much about opamps and there are so many choices. Any maybe an opinion ...
1
vote
1answer
70 views

How can the differential pair have individual common mode gain?

If you think of a better title, please do edit or let me know to edit, but this is how I thought I could word the question. I am finding difficulty in understanding how a differential pair exactly ...
0
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2answers
145 views

voltage source vs. current source

I am just not sure that why in development labs, current sources are not as popular as voltage sources. I have worked in different places, and they all have been using voltage sources. I just want ...
1
vote
1answer
57 views

Finding the thevenin resistance

The task is to find the thevenin equivalent (seen form terminals a and b) of the following circuit: I believe I have found the thevenin voltage by simply finding the voltage drop over the 5 ohm ...
4
votes
4answers
719 views

Charging phone battery with a high current source

I am working on a project which the goal is using some android tablets to show pieces of video file to form a multiscreen. One electronic problem that I have faced is: The tablets should be always ...
2
votes
2answers
251 views

Single current source with parallel loads for many RTD sensors

I'm trying to build a circuit that contains multiple 3-wire RTD PT100 sensors (12 of them). I have a microcontroller with plenty of ADC pins so I could potentially measure the RTD and the wire ...
2
votes
3answers
238 views

How do you drive a high current load from a moderate current source?

If I have a power supply that can supply 5A @ 12V and I need to be able to supply an inductive load with 20+A @ 12V, how would I go about this? I need a burst of current for about 2-5 seconds. Will ...
1
vote
2answers
96 views

What defines a source of power, the current or the voltage?

I have an apparently simple question, but I can't seem to figure it out. I learned in school that the generators (source powers) are defined by their voltage, and that made a lot of sense to me. ...
2
votes
2answers
169 views

Consistent LED intensity from low and variable voltage supply

I want to light 1 red LED among 3 (or no LED at all; never 2 or 3 simultaneously), using 3 output ports of a micro-controller (PIC18LFxxx or so). The catch is that I'm operating from a low and ...
2
votes
3answers
271 views

Steady State RLC Circuit With Dependent Current source

I'm trying to figure out the reason why in the following circuit, at steady state, the current ix is zero. My best guess is that because there is a parallel branch which by KCL should equal 100ix and ...
2
votes
2answers
198 views

FET - Source follower utilizing current source to lower voltage offset

I understand that if I use a FET as a source follower, the signal will be slightly attenuated due to the fact that there is some small inherent resistance in the FET, creating a voltage divider effect ...