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759 Threads found on edaboard.com: Current Source Circuit
I understand that we use an NMOS to form a constant current source. My question is, can we create a constant current sink using a similar approach with PMOS? Is constant current sink even a thing? Constant current source is a term used in the circuit theory (...)
Are you certain that you wired the actual circuit correctly? You may have the MOSFET body diode voltage drops to account for (2) when current is flowing in RL, e.g. the pin "2" of RL is not actually at ground (potential of the negative plate of the DC source) but diode drop above it). Take a DMM and measure voltage drops around the loop.
Are you saying that through this spiral does an electric current pass (ie the wiring is part of some circuit consuming power), or is it just a helical-like antenna ? If you want a 'stable' 50Hz noise source, I would recommend to make some circuit that you could predict the electromagnetic flow and even tune it. An open (...)
It depends on the loudspeaker and how much power you want. Some NE555 manufacturers specify as much as 200mA sink/source current which is enough to drive a medium to high impedance loudspeaker directly. The mass of the loudspeaker cone will be enough to average the PWM back to an analog level. For higher power all you need to do is ensure enough '
Hi! I am designing a PFC circuit(in boost configuration, inductor is CCM, switching frequency is 100kHz), and it has a high current spike during on and off of the MOSFET switch. I used a bulb as its load. I am not sure if these high spikes are results of the MOSFET parasitic noise or a common mode noise injected at the input of the PFC (...)
Because you are looking to run two equal currents through devices at two unequal current densities. So you need unequal areas. 1:N ratioing is the IC designer's best way to get a maximally consistent ratio. Drawing two different device geometries (like a single 1X emitter, and a single 16X-area emitter) puts you at the mercy of various lithogr
Power Supplies have normally a current limiting mechanism but if that one hasn't, you may limit the current by using constant current source principle by aid of voltage regulator ICs however some voltage drops may occur.Look at this IC and you can take some inspiration on page 18.
The transistors in red boundary are nothing but a simple single stage opamp. The final transistors(common source ones to the right) are used to add the current from the pMOS and nMOS differential inputs.
I have a simple low side switch using a mosfet for an Inductive load. All works quite fine. Now I need to add over current protection, and for this I need to add current sensing which will notify the driver or any other IC to switch off the mosfet if current is, for example, above 1A. 135546 I read many articles about it
Problem Statement:- We are current working on testing of different benchmark circuit using Tessent , DFT Advisor, Fastscan (Mentor Graphics) tool to calculate Test coverage, Fault coverage and ATPG effectiveness, We have calculated above parameters using default ATPG , but we unable to apply external test patterns to improve TC and FC. Whether
Since you seem to have a semi-infinite series of the most basic questions I think a textbook is right for you. But the textbook isn't going to teach you to recognize, for example, that "Vb" in the lower is the exact same thing as M3:M4 common gate node in the upper, only difference being whether or not the biasing is shown and how complicated i
It looks like an erroneous schematic. Presumed Q1 is a regular NMOSFET as claimed by the schematic symbol, drain and source terminals are interchangeable, and in this case, just drawn wrongly. After fixing the symbol, you get a regular current mirror with an additional resistor R2 draining part of the reference current. Wonder if the (...)
The obvious choice will be something like the LM317, but if you don't have one at hand, you can make a very simple current source like the circuit shown below. If you make R1 or R3 variable, you could adjust it between 10 mA and 20 mA. The switch is just for illustration of the minimum and maximum range.
currently have a relay thats rated for 15 amps for a 5amp AC PSU power source (high capacitive inrush current). I have it wired so that its in the NC state, and when the relay is powered it cuts power to the PSU (reason I want it like this is if the relay control logic fails on boot/power on, the AC circuit will still be (...)
One way is to use a programmable current source to vary the slew rates as shown below. A lot will depend on required frequency, level, etc.
If you overload your voltage source and it does not have current limiting then the circuit will smoke and burn or blow a fuse.
The "problem" is that even if the FET turns off instantly, the rise time of VDS will be determined by its drain source capacitance (Coss) and the load current. If your load is just a 1K resistor, this will result in a fairly slow rise time of VDS. You need to increase the load current greatly to see the true switching times of the FET. (...)
Even if both currents would be exactly equal, the circuit doesn't generate a "voltage window" rather than a voltage difference V1-V2 with unknown & floating absolute voltage somewhere between 0 and 5 V. I'm not aware of ready made controllable current source ICs in the ?A range. I designed similar (...)
hi, A P MOSFET requires negative voltages on the Gate and Drain with respect to the source in order to control source to Drain current conduction. E
Hello! Just a first hint for you. A thermocouple does not deliver a voltage but a current. You should search for a current/voltage conversion circuit. Dora.
With a series capacitor between the (current source?) and the upper RX terminal, it doesn't look much like a resistor to me. The mentioned photoFET optoisolator is only linear for maybe +/-100mV and then rolls over. Not a good general purpose "resistor" for anything but true small signal (as the datasheet itself makes plain). I wonder about some
Finding shorts by measuring voltage drops works quite well with PCBs, except for shorts between continuous overall power and ground planes. You need a constant current respectively current limited voltage supply to source a short circuit current that doesn't damage the board or components. A few 100 mA to (...)
I presume the TLP cathodes are directly connecting to STM32 IO pins? STM32 GPIOs can basically source or sink the required TLP drive current. But the circuit is completely wrong. - individual series resistors for each optocoupler required, power supply must be 3.3V - high side drivers can't use common power supply, need either three (...)
I think the circuit may be from "Op Amp circuit Collection", AN-31, attached is the schematic which uses LM102 and LM107 for a "Bilateral current source."
It is a differential circuit. The voltage across the shunt tells you the current across the shunt. That's a differential measurement. Common mode refers to the absolute voltage of the shunt with respect to ground. The diagram captures it well. The + and the - are the differential measurements. The voltage source shown is common to both (...)
Hi guys, Can we do the thevenin equivalent on a voltage divider where the voltage drop controls a voltage controlled current source? The circuit comes from two BJT small signal circuits with their emitter connected together. So I was thinking if it is possible to apply the thevenin equivalente at that input. Reagrds.
Yeah, I forgot the negative sign, because the current k*V1 enters in the negative polarity of the R3. Regards.
It could be measurement error. Your scope probe needs to be using tip and barrel only across Vcc and Gnd .... ~ 1cm or less apart without gnd clip. since ESR rises with C, the RC time constant is 10us for LOW ESR and about >>100us for standard. So when cable capacitance is switched current pulse causes a voltage spike at source due to ESR. BIt m
Comments: The time constant of 3.3K across 0.22uF is too short, you will get quite a lot of ripple. I would suggest you use a higher voltage capacitor before the voltage divider (after the bridge rectifier) maybe with a low value resistor (~1K) between the bridge and cap to limit surge current. That cures the time constant problem without making
Substrate diodes and dedicated protection diodes are forward biased with inverted power supply. If the supply source is able to exceed the maximum diode current, the device is destroyed.
Hi, I am designing a circuit that has GPRS communication. The modem has an STATUS output but datasheet mentions only how to put a LED as in indicator (standard connection when LED is in collector side with an 300ohm resistor and emitter is connected to GND). I asked manufacturer if I can connect STATUS pin to the microcontroller PIN configured a
In the circuit you showed the current source is set to generate a current from 10 uA to 100 uA in 10 uA steps. The setting is given directly in the I source where you have written "IBB uA", so any number you set IBB is in uA. If you prefere, you could also delete uA from the I source (...)
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.
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) The question appears to be incorrect, or perhaps unclear. Are you meaning you want to control the driven current of 6 LEDs in steps of uA's
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
"Pulse" refers to the square wave current waveform in case b, I presume. It has been already explained that the waveform is cause by connecting a current source as load, which is more a theoretical model than a real load case. You can however come quite near to it by using a large inductor with series resistance as load.
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