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727 Threads found on edaboard.com: Current Source Circuit
Hi, i want to make a digitally(FPGA) controlled negative current source. C1 capacitor is the load. - i want that current change equally for every single bit , for istance 1110 = Ix 1101 = 2Ix 1100 = 3Ix... but in my circuit current doesnt change propartional. i arrange resistor values to make it 2Ix (...)
Some external circuit will be needed - current source loaded to capacitor.
It's a standard cascode current mirror as described in any analog design text book. Plus two apparently useless transistor sourcing additional current to ground. You would want to review the place where you quoted the image for an explanation.
In first place I thought that this would't work, because you're forcing the current and by definition gm = did / dvgs. If id is constant gm is equal to zero. The same goes for the gds = did / dvds. Even though I tried to simulate that circuit and I get a completly different plot: 129410 The devices I am using are 1.
Hi Everyone, I am using MCU C8051F972-A-GM in my project . I have 6 LEDs in my board connected to the GPIO pins of the MCU. I want to design a circuit for constant current control with supply current in uA(when all LEDs are OFF) and with PWM dimming. I searched for the Constant current LED drivers with PWM control, but (...)
Hi, assume there is a simple connection of an ideal voltage source with a resistor. on the other hand, there is a current source connection with a resistor. I want to measure the resistance in each circuit. now, 1- for measuring resistance of a 10k or higher, it is preferred to use voltage source or (...)
I use LTS 25-NP current sensor to measure ac current grid. I just built it. I tried to calibrate it using simple circuit consists of a single phase source and high power resistor. The current is flowing when I change the source voltage as appearing in the Ammeter but the output voltage from (...)
Yes, you cam make your own A/D converter, and it's not too dificult to understand. With a constant current source and a small capacitor, you can generate a saw teeth waveform, which can be used to compare with measured signal. The time elapsed to reach the same value is proportional to the voltage.
There's no Vin, gain (transimpedance in this case) is measured with current source I1. Seriously I have no idea how the circuit is intended to work as oscillator, respectively don't know which transimpedance value you want to achieve.
What is I1? Are you really supplying the DC bus with a current source? That's weird.
Hi i want to add noise to the input current source of my multiplier circuit and i want to run the DC analysis. Can anyone tell me can is there any noise file already written that i can obtain from cadence or do it have to write a file of my own and include the txt file. Also once obtained can anyone pls tell me how to include it. In the (...)
Hi, All this depends on your circuit. You should give at least your example circuit. * Supply voltage? * output current? source only? or sink too? gain: How much gain do you need? What is the input voltage? I estimate it should be a unity gain buffer, am I right? BW: For me a reference voltage could be considered to be (...)
Ideally, SW3 should not be open, otherwise I current source would generate an "infinite" voltage accross its terminals.
Any circuit diagram to measure direction of AC current using PIC microcontroller (18Family) ? i.e, If direction of current changes the output of circuit should be changed from (high to low) OR (low to high) Thanks
Hello , Can someone please explain why the current at the output is considered to a pulse?? I don't understand how this the case if out input voltage is sinusoidal, or is the pulse obtained not necessarily the output? Please refer to the document and the schematic attached htt
for these super low frequencies, use a current source/capacitor ramp generator circuit. Start the ramp at the positive going zero crossing of the input sine wave, and reset the capacitor to 0 Volts at the negative going zero crossing. Save the peak ramp voltage value in a simple diode/hold capacitor and read off the voltage from that hold (...)
I presume you are referring to the circuit linked in post #1 126146 I would suggest some modifications. If no FET is available, you should at least use a Darlington (e.g. BC517 for the NPN configuration) to keep the base current error negligible. Secondly, the output transistor involves a voltage gain for Rsens < 5
Yes the internal resistance will limit the current in addition to any external resistance. Frank
Not sure what you are trying to do there. If you are trying to turn the current source on and off, I don't think that circuit is the way to go. If you're trying to do something totally different, then you're on the right track. If you're trying to pulse the current from 0 to 1A, then drive the INPUT of the opamp. In (...)
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).
... For proper operating point a large inductor i.e. 10^9 should be connected at output with a voltage source. I am confused what changes will this bring to the circuit simulation. As said in the following text (by Tietze-Schenk), this is a method for simulation to keep the outputs (of a fully differential
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?
With a ground side current sense under the load and feedback gain Rf instead of unity (Rf=0), you now have a VCVS where you define the V/mA ratio based on Rf.
Use a current mirror. If this advice isn't enough for you, show your circuit!
You wanted to know how to calculate the output voltage of the opamp. It is impossible to calculate because Mosfets with the same part number have a range of gate to source voltages for them to produce the same current. The datasheet for the Mosfet states only the gate source voltage to barely turn it on (the threshold voltage which is also a (...)
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?
circuit 1 is unstable without additional feedback loop compensation. circuit 2 has errors, as already mentioned. circuit 3 needs darlington transistors or additional current gain for high output current. Consider OP output voltage range and required supply.
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 MO
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.
I have played some with those EPC FETs (designing a very high frequency capable driver, at my last straight job). I found that their switching behavior on the high side depends greatly on the source impedance (kind of a "Duh!", but still). The gate-source charge displacement current needs somewhere to go, and quick. Point being that you (...)