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672 Threads found on edaboard.com: Current Source Circuit
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
1. The third OP is acting as a comparator (the integral of a triangle would be hardly a square wave, by the way). 2. It's a voltage rather than a current source. 3. The first OP forms a schmitt-trigger. The overall feedback is negative, the combination with the schmitt-trigger makes an astable oscillator.
pls explain me the working of this circuit.The text says that current source Q1 functions as usual but with collector volt- age held fixed by Q2's emitter...i.e the collector voltage of Q1 is held fixed by action of transistor Q2.But what i didnt digest is that if the temparature changes then the Vbe of Q2 changes resulting in a change of (...)
A PV is essentially a lossy current source that has a zener like open circuit voltage, Voc that declines slightly with lower solar input. The maximum power point is approximately 80+/-5% of Voc when the VI product has a shallow peak in power about this centre. You can hunt for this peak using MPPT regulated current sinking (...)
Hi, I don't know what you mean... To drive a LEDfrom a voltage source you need a current limiting resistor. Because the bias voltage is high in relation to a LED forward voltage the output (light) will be about proportional to input voltage. Klaus
In a RC circuit, if the voltage source is a sinusoidal source, I found the given equation. C is constant. I tried to solve this problem in time domain. So, I use a source in an EDA tool. I found the current in time. I know the voltage. I use simple numerical derivaton df(x)=/(x2-x1). In this case, (...)
If you assume that the current source has an internal energy source (an ideal current source in a simulation of course has), you don't need Vdd. A technical current source, e.g. a transistor circuit will need an external energy source. - - (...)
What do you think about the next current source? It has to drive a current, in RL, of 0.1 the most exactly it can be. For that, I put a transitor which has a Vbe= Ic * 6.8Ω ; so if the current of 0.1 goes up, the transistor drives and the currents goes down. The hfe of the transistor are 256. (...)
Let the voltage across Rx = Vx and battery current , I. Then V1 = (4k7/4k7+2k) X Vx, re arranging gives Vx = V1/(4k7/6k7). So 3.3 V = (100 X I) +VX, { 100 X I = volt drop across 100R ), rearranging, (3.3 - Vx) = 100 X I, so I = (3.3-Vx)/100. So I is the current from the battery, some flows through the 1K (Vx/1K), some flows through the output
Hi All, if I want to play with the PSR of a circuit block(for exmaple, op-amp), an AC signal is injected into VCC, and I want to use an ideal ac gain block to amplifier this AC signal and convert it to a current source. Would anyone teach me what is the easiest way, to implement Vin(ac) to Iout(ac)? Thank you! 114937
Hi, I am recently assigned to a project which is highly related to power management. The problem is simply like this: There is a circuit that already works but it is wanted to work on some areas constantly have power line down issues. So, I need to design a power management circuit that will always work with or without power line. When power goes d
Transistor current in flyback is unipolar sawtooth waveform. Where do you see current through body diode?
You should first tey and find the threat source or info about it (if this is a field return). Then, what you mean by "burned out" along with what you know about the event, may lead you somewhere. Those zeners / TVSes have peak current and short term average current and short/medium term power limits. An ESD event of classical form (...)
Hi all, I want to control the Bias and Modulation current of a laser diode using a microcontroller, a DAC and discrete components (including operational amplifiers). current range 3mA to 25mA with 0.1mA step. current pulses: rise time few nanoseconds, 10% max overshoot I have found this circuit from TI that controls (...)
Hi, I am trying to design a current starved VCO in cadence, i tried some circuit and it is oscillating, but i don´t know how to vary the input control voltage to get the oscillation frequency from maximum to minimum. i am attaching the png of my design. Any kind of help is appreciated regarding this concept. Thank you.113
If you just want to shut-down Vout -> 0V , it's enough to connect the power transistor's gate with its source - by a transistor switched via the enable/shut-down pin. Should you need a total 0-current shut down, you'll have to disable some control current, plus, possibly, inactivate some extra enable transistors. For more detailed info (...)
Other than Vref, this design has no input and the current sense has open loop gain so it doesn't matter what Vref does. What is the point?
In the circuit you have an independent current source (the left-most), a current source that generate a current of ampliteude depending from the current flowing in the 2 ohm resistor and two resistors in parallel. You need to apply Ohm's law, but also Kirchoff's law. The (...)
Almost all Mosfets are power Mosfets. You forgot to tell us the maximum current that you want in your Mosfet. Most Mosfets need a gate-source voltage of 10V to fully turn on (but 'logic-level" Mosfets need only 5V) so you need a gate driver circuit to boost the 3.3V from your microcontroller. The gate pulses to the Mosfet must be much higher (...)
Hello, Can anyone suggest a simple current reference circuit for a two stage op amp. I need to generate constant current in uA range to be injected in the diode connected transistor and mirrored at both the stages. Thanks, Hobbyiclearner
Left circuit is well known Widlar current mirror.. Right circuit is a voltage controlled current mirror/source..
AC has to be scaled and shifted and then measured. DC has to be scaled and measured. Same for current.
It's a simple cross-coupled LC Oscillator with Noise Filtering (by order to simulate such circuits, a start-up simulation trick should be used to excite the oscillator. For instance a step-up current may be injected into the circuit during a limited period or a step-up voltage source can be used to excite the (...)
To get a DC current as high as 1A and using a frequency of 200kHz then the coils will probably be fairly large and/or have a ferrite core. Since the coils probably must touch together then why not use a plug and jack?
For a LED driver you need constant current, not constant voltage. This is because the LED forward voltage drop changes with temperature, if driven from a truly stabilized voltage source would cause large changes of current through the LED. The total voltage drop might be around 30V, but what the 10W LED needs is a constant 333 mA. Frank (...)
In my IC i only want to use MOS for to design various component. In this how will i make current source?? Also describe in MOS, if source is connected to gate thn what is the significant of this type of circuit ??
555 is spec'd to +/-200mA output. With max rated at +/-225mA. Meanwhile, your R8=10 draws 1.2A spikes. Bad form. FET needs high gate current only to switch internal charge then low current. To improve you need to buffer the 555 such as complementary source or emitter followers, then R8 can be reduced to 5 Ohms or whatever max Gate (...)
I want to measure resistance and capacitance at Y port Connect a unit current source with ac magnitude=1 and any frequency between your output and gnd (separated by a large cap, e.g. 1F, in order not to short-circuit the DC output voltage). Then run an ac analysis, sweeping the frequency between your points of inte
Attached is a LTSpice circuit of a simple constant current source. A standard pnp / zener arrangement. I've used this circuit years ago , but I don't remember it being as good as the simulation suggests. Set for about 1mA output , it only varies by 25uA with a temperature change from 20 to 80 degrees and a load change (...)
Your schematic uses what look like current sources. A current source will generate any voltage necessary to push its specified ampere value. It will even generate a very high voltage. Could that be the cause of your odd readings?
Can you give the circuit that you are using for your experiment? At what voltage is the Gate and the Drain set at? It seems that when you enter the Cut-Off region, the Drain to Body diode turns On and you see a current gain. I'm just guessing.
Hello, Please need a suggestion on Plating thickness tester. currently working on the project. As you know there must be constant current source constant current source for the application. So how can built or Is any ready made available in the market. because i don't have luxury time to built my own (...)
the circuit works to keep the voltage at the base constant in that case I think its much more the emitter voltage that is beeing held constant by varying the base current!
What is defined as 'reset' condition for your circuit? What is the intention of the 'load' circuit? It looks like a variable heat source (RV2, Q3) with a fixed current. What is the MCU you are using?
To take a more accurate answer it is necessary to know the current waveform, or circuit topology.
The common mode setup isn't yet right. The current source must not be connected in series with the load but between ground and output. I suggested to use a load with center tap for symmetry.
Best intelligent charge monitor will pulse battery with light load and heavy load and compute C, capacity based on load voltage and ESR. For example using programmable current source ,pulse 1st 5 mA then 505 mA and use S&H to display ESR or delta V over delta I (0.5A) which is a function of C the Ah capacity of battery. Each battery chemistry has
I think that your circuit above is actually better described as a constant current load (or source) - the transistors in the bottom are setup to try to draw approximately 260mA through Q2 regardless of what the top connected power supply voltage is, with the only other limiting factor besides the output level of the power rail being the (...)
Here is a website (one of 100's) which has several constant current source circuits. Note that simultaneous control of output current AND voltage basically implies a very specific load. However, I assume the voltage range is the input voltage range, so no problem there.