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709 Threads found on edaboard.com: Current Source Circuit
Hello, I have been tinkering with the constant current sources recently and want to drive my 30 W LED using it, I have simulated the circuit below and it seems to give me the correct current. Basically the current source (1A) is created using the OPAMP circuit, but I (...)
I'm trying to replicate this circuit for a 2W laser diode engraver. I could understand most of the other components except the current source schematic (Pg. 5, Fig 4). I understand that the TLC271 is being operated in high-bias mode (cause the
I think it's a 'long tailed pair' inverter with a constant current source in the combined emitter connection so it gives maximum voltage gain. Exactly why that is necessary isn't clear unless it's to ensure the drive signals to the IR2110 switch abruptly between logic levels. Brian.
Make model as CCVS(current Control Voltage source) or CCCS(current Control current source).
Hello, I am simulating differential pair with current mirror and current source (attached image , top is with current source and bottom with current mirror configuration) and I have confusion regarding operating point. I am following Electronics circuits book by tietze (...)
That may be because, your testing circuit is taking lot of current from the power supply. What amount of current is needed for your circuit ? What is the rating of your power supply?
I need current source 0 -10mA for measure PTC thermocouple (various resistance) This means that the load must be grounded! I use any as (see pic)with digital potentiometer and LM4041, but it is complicated for me and I I am seeking something that would be to drive DAC 0 - 2.5V An idea for a simple voltage controlled current (...)
Use a current mirror. If this advice isn't enough for you, show your circuit!
I feel that the questions in your post #1 are essentially unanswered. 1. Yes the RC circuit will affect the rise time if the circuit is operated with a respective fast control voltage. Obviously the circuit is designed for static constant current, so it doesn't matter here. The purpose of the RC circuit (...)
Some of the schematic is missing but relevant to the explanation. For example, it appears to have 4-wire resistance measurement but unless R314 is supposed to be connected as current source the schematic makes no sense. From what I can make out though: 1. K301 is part of the voltage ranging, possibly driven during auto ranging routines. U301 see
Hi mates i am using howland current source to convert 1-5 Volts to 4-20mA; I have tested attached circuit in multisim it works good (as can bee seen in table). However I have put the same circuit on general purpose PCB but i get results as: Volts output current 1 (...)
Hi, you may also consider this circuit as a 'current comparator'. Esentially, the Vout vs Vin plot will be really similar to that of an inverter, but the triggering voltage will be shifted (determined by the sizes of the devices and the bias voltage of M2). Really, the output is High impedance and the exact voltage will be hard to be defined. For
Make a drawing,schematic of what do you want ... Wich power to put ON / OFF maxi current on 30V output ? so you will not cut 230V AC .. because of using 30V -> regulator -> PIC power supply nota : How do you control 5V PIC from 30V DC ? IOverheating or desctruction risk if using glassic linerar regulator as 7805.. simplest is use of a Relay .
It may be possible to source enough current for Vpp but bear in mind this design can only program devices in LVP mode and out of circuit. For the sake of a few extra components it can work in LVP and high voltage modes. All I can say is this design would be banned from my workbench ! Brian.
in this circuit, how could i apply an appropriate DC bias to keep all 12 MOSFETs in saturation? Your circuit is already biased via the 20?A current source. If this is a correct value depends on your process and its model files. You'd perhaps have to adjust the current value and/or some W/L ratios until (...)
A short look on the corresponding common mode gain formula Acm=gRc/(1+2gRE reveals that a common emitter resistor RE is necessary to ensure a low common mode gain. However, a large ohmic resistive part would - at the same time - also increase the DC voltage drop (and require a very large supply voltage). For this reason, it is wise to u
I have a current source with precision value of current. The definition of a current source is that it delivers an unchanging Ampere level, regardless of what component is in the path. I guess you are talking about the bias current? The B-E junction is a PN junction which drops 0.6V. (...)
Hi i am just starting to learn about layout design. I am trying to do the layout for a circuit. In the schematic i have run the simulation using a current source. The current source positive is given to the gate of a nmos and the -ve terminal of the current source is (...)
Dear all I've been playing around with simulated equivalent input current noise in LTSpice and I found out that, in the same way it works when you have two DC current sources in series, the maximum current noise you get is the one set by the lowest contributor. For example: In a simple circuit based (...)
..... Finally what is the difference between voltage and current source. Both are making current flow through the circuit. ....... In simple terms, in a voltage source, -- its magnitude is constant. --the magnitude of the current flow is determined by the components values (...)
Hi all, if we have a current mirror to generate a current source signal or sink signal, with repetitive rate frequency, such as sine wave, are we able to apply some low pass filtering circuit directly to this current, and generate a close to DC level current? Thank you!
You'll find a detailed discussion of the cascode current mirror in analog design text books, e.g. Razavi, Design of Analog Integrated circuits section 5.2.
How do I calculate Vout/Vin of this arrangement: 121875 I have to do this using the small signal model, I am a beginner level electronics student so a complete explanation would be nice. Replace the MOSFET with its small signal model. So you have a current source from drain to source,
The purpose of your circuit isn't obvious. Q2 is the output side of the current mirror. What do you want to achieve by feeding another current source to the output?
witch is a better solution 1 , 2 or 3 of course 2 may not work another question is that T2 in circuit1 are act as base current source or
If we want precisely matched PMOS and NMOS current source, for example, they are both equal to 100uA, which kind of circuit can match them well? thanks.
Leastwise, all current mirror components will appear as noise sources in your equivalent circuit.
Without knowing the EMI immunity of the layout, you must consider the breakdown voltages for each terminal to protect it from excess reverse voltage One diode could be used for this purpose especially with inductive lines and open circuit with current. Keep the current loop small in area with coax or twisted pair and you may still need a CM (...)
(1) It's a trick to calculate the Thevenin resistance. Feeding the circuit with an auxiliary source, find the current and then makes R_{th} = \frac{V_{aux}}{I} But solving the circuit in that way is the worst idea that a human can have. Note: I_l + I_s = I_l + \frac{V_l}{2} = \frac{3 I_l - V_l}{4} \;\;\long
Your circuit may work but there are several problems with it. First the third gate output should not be directly connected to transistor bases but via a current-limiting resistor. Second, MOSFET gate should be protected from an overvoltage, typical maximum gate-source voltage is 6V. Third, with the inductive load the MOSFET channel should (...)
Hiii all, For constant current source circuit,can I use any type of op-amp? or in other words all op-amp will support constant current application? In my project I want to give constant current of 1.5mA to a pressure sensor. Thanks in advance.
try lower Rds on mosfets with lower gate charge, try a 45% duty cycle, try increasing the resonant freq of the ckt so the mosfet turns off as the current rings down to 20% of peak...
If you put an unidirectional TVS diode across low-side MOSFETs drain-source, it is going to act as a freewheeling diode (being faster than MOSFET body diode) and, depending on the freewheeling current, it might fail. @FvM: The TVS diodes are really fast (1ps) hence they could limit the voltage across the MOSFET drain-source before the (...)
Can anybody explain the output current and voltage waveforms for the bridge rectifier circuit?I could not find it anywhere.....I have attached the circuit
Very confused question. What does "if I use a DAQ board which has a digital pin output from 0 to 5V, for this application, can it source the current & provide the negative voltage necessary for my circuit?" even mean? First of all, yes a power supply can supply negative voltage if the (+) and (-) terminals are isolated from ground. Like (...)
I was thinking something like this for adding the modulation current: 113699 Will the switch cause spikes in the pulses? What Voltage controlled current source do you propose? Does some one has simulation model for laser diode? plz help
i tried to implement a multilevel inverter. i done already in matlab which shows what i want. during the hardware implementation the output voltage shows the same result as in matlab if load is zero. when i connect a load the output voltage becomes zero no current flows through it.why this problem occurs. the sources are 3 nos of 12V battery whic
The equation Ve=... is not correct. This equation assumes that Ve is determined by Vx only - and you forgot the current source.
Friends, I would like to design a class E power amplifier. As you know, voltage and current waves of the switch in negative peak must be zero, but in my circuit they have negative values. When voltage is negative, current is positive!So, in this condition the switch can work as a source of power and can produce power!!! (...)
Sink versus source is only a different (more graphical) way to describe current polarity. Asking generally about "sink and source" current doesn't make much sense. The input or output current of device depends both on the external circuit and the internal function. A datasheet (...)
Hi, I'm using some chipset via USB which allows an input voltage between 4 - 20V In order to block 12V from injecting to the 5V power circuit I'm using a diode on the 5V supply. While this works fine with 12V (since the current is low), when I power the chipset with 5V the current is quite high which results that this diode is heating (...)
Would you mind to explain the purpose of the opto triacs in the shown circuit topology? Besides other problems, their current rating doesn't seem to fit the MOSFETs. The schematic is somehow incomplete, it's not shown how the gate signals are generated and if they are referenced to the MOSFET source terminals as required. If so, there's (...)
hi, how can I make a circuit with positive and negative voltage with high current. With such skimpy info, an informed suggestion cannot be made. How much is "high current" and how much voltage? Do either need to be adjustable? Does it need to be regulated? What is the power source?
Hi all! Do any of you know of any buck, boost or buck-boost constant current circuit that is able to regulate current more than 2A? Thanks!
Hi, I assume that the AC is mains frequency current? If yes, there are many possibilities. One is a current transformer, which gives total isolation of the measuring circuit from the monitored current. It is easy to implement. I have seen, that there are even cheap small current transformers available in (...)
Hi, I'm currently simulating a Flipped Voltage Follower. I've ran a transient analysis (pulse wave) and the output seems to show large voltage spikes. What could I do to remove this all together? or anything I could try adding to the circuit? any help is appreciated. thanks!! 117984
The most popular methods are to use a switched current source alternating from,sink to source at safe levels and looking at the response time for excessive capacitance which can signal an "almost short "in CMOS or a low voltage swing. Backdriving junction points incircuit are often done by ATE but this won't detect (...)
The transistors in such a circuit have to be complementary for proper operation. So the input transistors are typically NMOS and the load is typically PMOS. But it could be done with the input transistors PMOS and the load NMOS. Basically the drains of the two transistors have to be facing each other for the circuit to work since you need
Thank you so much BigBoss could you tell me where it comes from( Gm=Idss/abs(Vp) )? and how can we find the source-Drain current with specific gate-source voltage or vise versa ? It's not coming from somewhere, I have given a rough expression for that.There isn't a handy consistant equation for HEMT devices therefore
Hey guys, the following circuit was attached to a boost convertor and is used to provide a 2 MHz frequency square waves to the Boost Convertor. My issue is when looking at the circuit, I realized I don't fundamentally understand how it achieves that. 1) So for example I understand that the second Op-amp is an integrator (since it has a capacitor i