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737 Threads found on edaboard.com: Current Source Circuit
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 (...)
I now see the reason for the arrow in the current source. It is negative conventional current produced by a current source that must have a negative supply voltage since the base of the NPN transistor is at ground. If the gate of an enhancement N-channel Mosfet is also at ground then the (...)
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
No AC source is actually floating, and most likely you don't want to operate your circuit directly connected to the mains. A suitable solution for most applications is a high impedance (e.g. 1 Mohm to 10 MOhm) differential voltage divider. It involves some leakage current, but low enough not to trip any RCD protection or to expose (...)
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
Hi i have encounter an problem, how to set the unit for parameter sweep in the dc sweep controller. in this case i wanted to set it to "uA" as shown in my IBB current source. 130410 thanks
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.
Hi, Attached is a current mirror design I am a little bit confused about. I do not know what this kind of topology is called and thus cannot find any external information. I do understand that this is a cascade current mirror, but I don't know what are the two external transistors doing and what is the benefit of having them in design.
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.
Sorry,I forgot to update the current diagram and thanks for your "wish" erikl :popcorn:. After done some reading, I try to make some changes to the circuit. As I know, oscillator circuit need 180 phase shift (at least two poles). What I did actually is I'm connecting the first block of the circuit to another (...)
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 (...)
Hello all! I am using gpdk180nm CMOS lib for designing BGR circuit. I have designed the circuit using current mirror. But to improve this circuit I am using op-amp. I need to know what type of op-amp should I use for getting 1.12 V const ref voltage for temp range -40 to 125? What should be the gain, BW, PSRR, CMRR of (...)
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
If I induce a voltage v in a circuit with resistance r, will I get current V/R? I've always assumed there were some exceptions to this rule since 9V batteries have high voltage but do not give out high current... but rather than being an exception to the rule was this due to its internal resistance?
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.
i am trying to measure current in a simple circuit consisting a voltage source and a resistor. I have written a simple verilog-a code that shorts the voltage output port to resistor input port. while simulation with spectre a error: that the branches form a loop of rigid branches (shorts) when added to the (...)
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.