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Can you please be more clear in what exactly IS the question? My question is what configuration I should use with my IL300 to use it as a current sensor. You mentioned that I should scale the current using a shunt since the input amps range for coupler is quite low, should I be using a variable resistor? How sho
offset voltage and gain error terms need to support LSB accuracy. Bandwidth / settling time need to be well better than sampling rate, and settling time is to a very low residue error. You would have to design the amplifier for the worst case (max bits, max bit rate) or cases (if your scheme varies them independently or according to some built
We are using the TCP303 current probe with TCPA300 current probe amplifier to measure DC average current. We are connecting the TCPA300 into a Lecroy Wavesurfer oscilloscope. The readings are coming out much more inaccurate than the ?+/-3% of reading? suggested in the current probe datasheet. The current waveform that we are measuring the
Hi, currently im making an IGBT protection for voltage inverters - by turning off PWM signal in right moment. Now im making PCB and because its my first big project I have some questions: 1. I want to use TLC3702 comparator, they say that it has build in push-pull.. so i dont need any other resistor for it to work (besides current regulations ofc
could I just use a transformer from mains and then rectify and supply to Vb as long as the transformer supply voltage is higher than the H-Bridge supply? No. Vb must be held at a constant 12 to 15 V offset (=VCC) above Vs, the diode is achieving this in combination with C2 in a regular half bridge configuration (low side drain conne
1. I can suggest you to use an OPAMP with very low input offset voltage (also known as Chopper or auto zero or zero drift. the name varies with manufacturer but the functions are same). Non of the OPAMP which is embedded into the microcontroller will suitable to interface your sensor (except Cypress PSoC controller wich is very much expensive compa
hi, I would like to sense the current from a path where a current of 50mA to 2 A is flowing to the load. Can I use simple differential amp with gain across the Rsense =20mohm or is there any contemporary design help. thanks
In order to prevent self heating errors,current shunts are typically 50mV full scale for 20A. But for 200A , I suggest 5mV drop for 1W dissipation. Then use low offset high CM Op Amp or special Current sense amp, Try to work around this instead. This means 250uΩ using wide strip for low inductance and good heat dissipation. The current (...)
Apparently the TINA LF444 model comes with 10 mV built-in offset. According to datasheet it's rather a worst case than a typical value, but not impossible with this cheap general purpose amplifier. A straightforward solution is to use a precision (low offset) amplifier instead of asking for "offset correction". In any (...)
I am designing a 4-20mA mosfet current source with power supply= 1.8v. with this power supply because of the large current passing through mosfets, I have to choose big channel width for the mosfet which have been used like 45um or 30um. I can reduce this amount using a power supply much more than 1.8v like 3.3v causing to increase the value of pow
Hi Guys, I'm looking at a design from TI, I noticed that they have used a cap and resistor on the transformer primary side, to eradicate any DC offset seen by the transformer. 128979 Documents Documents Schematic
An integrator uses maximum DC gain not unity , so it does not need to be unity gain stable. It does need to have very low DC offset. You may be confusing the fact that Op AMps are integrators with internal small compensation and are thus often unity gain stable. When they compromise compensation for bandwidth, unity gain stability is compromise,
The OP07 opamp you're using as a comparator is not very fast. Its main claim to fame is the low offset. I expect an SR flipflop will more than be able to keep up with it for speed.
Its datasheet is published by its manufacturer and it says the max gain (with all spec's) is 1000. Don't you believe them or do you want poor spec's? Simply add a cheap low noise opamp to its output. The extra amplifier does not need to be an expensive instrumentation amplifier.
Unfortunately, the question can't be answered by applying datasheet information. Particularly no output impedance is specified, so you can't tell what's the maximum transverse current caused by buffer offset. I would expect that it's usually low. To be on the safe side, provide a series resistor option (0.5 - 1 ohm) and replace it by a short if
Having a high impedance and input current input load is good for low input offset voltage amplified by high gain. Ensure you calculate this effect in any choice of input DC termination to a reference voltage , be that 0 or V/2. Also allow for leakage effects from dust and moisture , which can often be << 10M in forced air environments and (...)
140dB (!!) is a voltage gain of 100 million. Then an OTA with an input offset voltage of 5mV will produce an output of 500,000V when its input is zero! What about low frequency noise being amplified 100 million times? Don't be silly.
Yes, You could add a DAC at the the node named Va in the above picture, you will have to add current sourcing DACs and current sinking DACs on both sides of the differential halves (at Va nodes) to be able to handle any kind(+/-) of DC offset occurrence. Another way could be to implement a high pass function in the path with a very low cut-off fre
There are many choices and tradeoffs; cost, thermal offset, GBW, Noise V, noise A, avilability, etc Define your requirements for SNR, Cost, impedance , offset, drift, etc. then rank importance and then choose. also LT6230 - 215MHz, Rail-to-Rail Output, 1.1nV/rtHz, 3.5mA Op Amp Family Features low Noise Voltage: 1.1nV/√Hz (...)
what if input < 0 or > 2V? Use 0.2V Diode OR logic analog input so highest voltage is detected, then All you need is four Window detectors with 3 comparators and logic to gate when Vin > Vx and Vin < Vy Or use LM3914 with 10 levels and active low side driver/selector out. offset input by 1 Diode drop to 0V then calibrate to your thresholds and
Velocity is the integral of acceleration, a Distance is the 2nd integral of acceleration. Thus the "analog logic" is the continuous 2nd integral of the vector acceleration and reset between readings with zero reset time and auto-cal for DC offset using ultra-low input offset chopper type Op Amps as charge amplifiers. Any small DC (...)
I think it's more or less pointless to discuss the details of an obviously flawed circuit design. The circuit makes sense with a a low voltage (e.g. +/-15 V) supply, otherwise it seems to represent the idea to switch somehow +/- 200V, controlled by a low voltage comparator. As said, it doesn't work this way. But there are possible circuits and comp
same gain, difference is input impedance and output drive current Iout for rail-rail OP Amps is small ( due to high RdsON of internal CMOS output stage) so 10k may not reach 100% both rails if reference is Vbat/2, so >> 10k feedback R is preferred for low Iout. But if R values are too high, then input bias current offset may cause a Vin of
Your problem is partially due to inductive coupling of current pulses on an AC bridge caps. If your inputs are not low impedance or perfectly balanced impedances on both inputs and cables and source connected to it, the mutual coupling of common mode H fields from current and E fields from voltage capacitively coupled to high impedance inputs, it
The problem specification isn't very clear. Do you want a low (0.1%) modulation according to the input signal offset? Or reduce the offset to get maximal modulation depth?
Hi, 2k4 source impedance .. is in a range wher a bjt or a fet opamp can be used. I'd prefer a low noise bipolar opamp. Variable gain. You could look for automatic gain control, often made with OTAs, (compressor) Or you could manually adjust it wit pot. Or control it with microcontroller, e-pot, multiplying DAC, or special opamp with built in gain
hi az, Your proposed method is often used as a low side current detect circuit. Ensure that the 0V points for the OPA inputs are tied to the same point as the load resistor. I use the CA3240 OPA, you may have to trim out any OPA input offset voltages. Also the CA3240 will not swing to +5V if its powered by a single +5V, you could consider a MCP600
I read the book from Maloberti, which says that: "A charge injection into a low-impedance node will only cause a glitch whose duration depends on the value of the node impedance. However, a charge injection into a high impedance or capacitive node causes an offset that can be problematic, especially when the injected charge is signal dependent i
these connection are given and i am monitoring the DRDY/DOUT pin in the scope. will the DRDY/DOUT becomes low after conversion. Is SCLK low in idle state?
First of all, you need an opamp with a low input offset voltage, since that gets amplified along with everything else. For the MCP602 the offset is specified to be 2mV. That means with NOTHING on the input the output could be at 200mV. Since it's AC coupled that's probably not a problem. But, worse, that means your input may have to (...)
.....But from my circuit i think that pull up resistor (at output of opamp) make the output 4V while inputs are not given. Am I right ?? no. The comparator has an input offset voltage that could be positive, negative or zero so the output could be high or low or oscillating.
U1 output = 68/2.8 times the volt drop across R9 plus the offset of 1/2 Vs. the capacitor just is a low pass filter working with R3, C1, provides feedback at high frequencies, because of its low value it will be used to offset phase shifts within the op-amp and also provides a HF roll off function. Frank
hi, Connect a 4K7 or 10K from LM358 Vout to 0V and recheck the Vout low. E
Saj, You ought to specify the constraints of your designs. What is the input and output response ..... Let me help you get started. This should be standard practice for any design. Inputs1. from DAC. Analog, low Z 0~2Vdc - 10K series to Hi Z - controls Q1 current 10A/Vin 2. From Func Gen, lo
Hi I am implemented Gardner timing error detector(TED) in QPSK modem. I will hope this TED no have any response to frequency drift, But in real circuit It has some output specially in low frequency offset Anyone has experience ?
Hi, this page is about low pass filter. DC is the lowest frequency one can imagine. So it lets DC pass. Look for a high pass filter. This lets high frequency pass but blocks low frequency and of course DC. Klaus
sdmuashr, you have forgotten to tell us which power supplies you are using (single or dual supply)? In his first post he shows all voltages. The positive supply is +10.2V and the negative supply is -5V. With an input of 0.6V and an output of 5V to 7.35V then the voltage gain is low enough that input offset voltage doe
WHat is not shown is a gain control pot for the 1k resistor in the bottom right corner to ground. The 1st stage has ● HIGH OPEN-LOOP GAIN: 160dB ● low INPUT BIAS CURRENT: 10nA max ● low offset VOLTAGE: 75?V max The cap added tends to improve the phase margin and cuts lower than the internal cap put in all (...)
any method to design a low offset CMOS amplifer? Without the auto-zero and chopper, besides the large size of the transistors, any other way to realize low offset? Thanks, Shawn
It is a tradeoff between your signal requirements output offset , gain and input offset of next stage. I would expect cap impedance should be same as source impedance at f range and much lower than load impedance. But that too is a tradeoff with low 1/f noise and signal bandwidth.
Hey everyone, So I have this question: In a certain application an output signal with f=500 Hz is affected by a DC offset and a 400 KHz noise signal. Design, Simulate and implement a circuit that will cancel the offset and attenuate the noise signal by around 20 dB. Shall I design first a low pass filter or a bandpass filter. Because (...)
I am going to use a common Op-Amp configured as a differential op-amp high-side and low side current sensing to measure an AC load. The output of the op-amp go into the ADC of a MCU. I would like to ask is the offset voltage rating of the Op-Amp important when selecting the Op-Amp? Can I just subtract this offset from the reading in the (...)
If resistor values are high and board is uncoated, even relative humidity could make that kind of change. At such low input level, Vio drift and things like charge pumping of ambient 60Hz/120Hz hum could be at play. A copper box and a known-stable voltage meter might be a good thing to try. I see "520mV" and "530mV" as being a bit short of resol
The LM324/358 is not a good choice for your application. These opamps have bias currents (250nA) that will just kill your input measurement. For example. If you've got 250nA through a 100M resistor, that will drop 25Volts!!! You need to use a precision opamp with low bias and offset currents. I would also suggest you use a bridge circuit.
That's a low-pass, although I'm not sure what a 330E resistor is.
Hey guys, I was just wondering how i would make a voltage buffer/follower without using an opamp. I have used some class A (emitter follower) and AB amplifiers, but when my output is very low impedance, my output starts to saturate with an offset. I was wondering if you guys had any designs in mind with very high output impeda
Hai, I'm trying to interface a thermocouple to microcontroller. As the thermocouple produces very low voltage, I've given an INA126P instrumentation amplifier to amplify the voltage. I'm using +5V as V+ and GND as V- and Vref=2.5V. But, in the datasheet it says input common mode voltage is 1.5V to 3.5V (from graph). So, I tried to add an offset t
The capacitor value will be chosen for sufficient low AC voltage drop. Then the voltage across the capacitor will be almost constant DC (of 2V) and not reverse.
I'm not sure what the point of the Vref signal is, it just provides an offset to your output voltage; you could just as well make Vref=ground. So, Rref is simply the box labeled "low side current sense", you connect the resistor between the bottom of the H-bridge and ground, and Vin is connected to the top of the resistor.
Does anybody have Ultra-low Phase Noise Crystal Oscillators written by Everard and Keng. they offer -147 dbchz phase noise at 10 hz offset. I wonder how they achieved this performance.