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648 Threads found on edaboard.com: Current Source Circuit
You can safely forget about this approach. Don't expect to achieve ns pulses with closed loop feedback current source. Try something using transistor current sources respectively transistor as V/I converter. In a 10 ns range, GHz OP based current sources can be an option.
I think the input reference current changes the oscillator frequency.
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 ??
Dear All, I'm building a circuit using 555 chip to open and close injector. My problem is that if resistor R5 is any smaller value than ~700ohm, it gets very warm. If it's like 100ohm, it gets so hot that you cant touch it. Is it normal or is there something wrong with my circuit? I'm driving this circuit by 12V from J2. If I leave Q1 (...)
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?
Specifications. 1 Amp continous current. Voltage range of 0 to Vdd Control signal type PWM(Microcontroller output) current sense to limit voltage output . Voltage is supplied from 2 lithium batteries connected in series to give 3.6+3.6v Dc.
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.
CAN transceivers are also generally designed to be quite robust - they have substantial amount of current source/sink capability, and output short circuit protection. They are capable of handling the dominant/recessive bit battles on long cable lengths without incurring damage. Some of them have significant ESD and overvoltage protection (...)
Referring to post #6, you'll find a gain calculation in the text book from where you copied the amplifier circuit (Razavi or whatsoever). The transistor Id and respective gm is primarly set by the current source transistor M5 and only slightly depending on Vcm, as long as all transistors are in saturation.
hi, Its a 'current mirror' , look at this pdf for a description. E
Please specify purpose like switching speed, direction, current source and sink capabilities, etc. Analog Devices have a very good range of isolators. Link
Circumstances at your measuring place are of such nature that it is usuall to consider current measurement using current transformer instead of shunt.
Hi all, I'm building a circuit, wich I can't quite figure out, so any suggestions will be appreciated:) The circuit shall act as a constant current source for 3pcs Luxeon rebel leds (driven at 500mA as total for the 3, 166mA each) I need to be able to control the current downwards, by a analog (...)
One way of doing that would be to calculate the RMS. Another way, perhaps less time consuming would be to divide the energy dissipated by the time period. See the attachment below (Note that the definition of current in the attachment holds only for the first time period, but it is sufficient to calculate power from this, since current is a period
A Widlar OP current source circuit is a popular way to achieve what you want.
106337 The figure shows multimeter at the output is in Ammeter mode which i think it functions as short circuit for the system. Referring the picture, I attached. I have designed a series voltage regulator that can convert AC source to DC source (range from 0 - 20V). However, I could not achieve 5A maximum curr
The datasheet for the Cmos 555 ICM7555 from Intersil has graphs showing the typical output current. It can source only 2mA (but its minimum current might be only 1mA) and sink 10mA (or a minimum of 5mA) when its supply is 3V from two brand new AAA alkaline cells then you will watch the LEDs dim even more as the battery voltage drops to 2V. (...)
hi, Unless the grounds are connected the circuit won't work since the current has to flow back to the source. If your purpose of isolating ground is to avoid noise you may use ferrite beads(having attenutation at that frequency) to connect both grounds.
A fixed current source, a shorting switch and a capacitor is pretty much it. But getting the first and last, ideal, small and cheap, is maybe the harder problem. Do you really need a linear ramp? If so then an op amp integrator might be cheapest, I know of no good fixed current reference piece-parts. But in a closed loop setup ramp (...)
well, what IS its impedance? If it just looks like a slightly inductive short circuit, it will be hard to match to. Try driving it with a current source.
The "loaded Q" is the quality factor of the RLC circuit. The Q factor would be translated into a respective bandwidth fc/Q if you drive the circuit by a voltage or current source. For the bandwidth of the complete matching circuit, the 50 ohm source impedance must be considered, which about (...)
Perhaps you want to show the full simulation circuit including current source and probe?
Ids: current that enters the drain and leaves the source No - I don´t think so (because there is no difference between drain and source current). I think, the subscript stands for "short circuit" of the Vgs voltage (Id for Vgs=0).
The term "lock-in amplifier" doesn't exactly match the application, but a complex impedance measurement with phase sensistive rectifier is perfectly suited. In addition a measurement circuit that is insensitive to cable capacitances, e.g. voltage source/current sense. That's how all AC impedance (LCR) meters work.
Attached is the LTSpice ASC file of a simple voltage follower current source but the simulations are showing wrong results. The non inverting input of the opamp is set to 2V and the inverting input should technically see the same voltage while changing the gate voltage of the MOSFET. 100 ohm resistor is used as a load. Could i get help debugging th
Obviously, the capacitor charges with DC current from the battery. The amount of current is limited by the resistance. The capacitor voltage rises to about 63% of the battery voltage in "one time constant" which is R in Ohms times C in Farads. When the capacitor is fully charged then no more charging current occurs.
I need to measure the total amount of current being drawn from a voltage source in a circuit simulation. When I hold the cursor over the voltage source, it turns to the 'current probe' - but the arrow is facing in the 'wrong' direction so I get a negative current draw - as shown in the (...)
You need two transistors, one dc current source and load for your output transistor, e.g. vdc or resistor. Paste your schematic.
You did not say if the circuit must source 2mA or sink 2mA. You also did not say how accurate the circuit must be. In Google Images there are hundreds of constant current circuits. Simple ones are simply one transistor, a zener diode and two resistors.
That 12 volts will DEFINITELY be a problem. I assume you are trying to use the LM317 as a constant current source? Why not just use a diode in place of R4? This will: 1) Give you your 'bias' voltage 2) Protect the 317 AND the ADC.
Hello! I have a funny very basic but very confusing situation. 103047 I have the circuit you see in the graph: a tail transistor M1 has a set gate voltage C, so it's acting as a current source. The branch I care about has a current source (transistor M3, with gate voltage A set, so set vgs), so I (...)