Parameter. LF LF LF///B. LF LF Units. Typ. Max. Typ. Max. Typ. Max. Typ. Max. Typ .. This datasheet has been download from. These are the first monolithic JFET input operational ampli- fiers to incorporate well matched, high voltage JFETs on the same chip with standard bipolar. These are the first monolithic JFET input operational amplifiers to incorporate well matched, high voltage JFETs on the same chip with standard bipolar.
|Published (Last):||22 April 2010|
|PDF File Size:||19.82 Mb|
|ePub File Size:||13.61 Mb|
|Price:||Free* [*Free Regsitration Required]|
Hi sixcab, thanks a lot for your very detailed reply and it totally clarifies what I confused about LF To have meaningful results, you want the dc daatasheet point of both the input and output to be about the same—after all, the bode plot never shows an exact 0 Hz frequency.
LF Datasheet(PDF) – National Semiconductor (TI)
This is probably a crap model, which is very common. Even though, your input source has 0 Vdc, you still amplify some dc signal—that is the offset voltage.
Following your point on the input offset voltage of 3mV of LF, I added such amount of DC value in my signal source of my original diagram and repeated the simulation.
feedback – LF integrator simulation using LTspice – Electrical Engineering Stack Exchange
For the LF this is spec’d at 10mV and this is being amplified by the huge dc gain of the circuit. Just to verify that I didn’t make any mistake when importing the op amp model, I did the same simulation with another op amp OPA and the simulation results were reasonable see image below.
You’d ideally use a large resistor in parallel with the feedback impedance, that way you can keep the offset voltage from saturating the output. Also, the greater the value of this parallel resistor, the greater the dc gain to the offset and risk of saturation. Let’s take a look. You can look at this answer towards the end of it or this videoit explains a bit more why this works.
Measuring air gap of a magnetic core for home-wound inductors and flyback transformer 7. Input port and input output port declaration in top module 2. They call it EOS in the model file. What is a Discussion forum? Sign up or log in Sign up using Google.
All of this makes me wonder if there is anything wrong with the spice model of LF downloaded from the TI website which seems not likely or if there is something about this JFET input op amp I didn’t understand not suitable to use for integrator circuit.
Look at the location of the ac source now: Now, this is a method a use sometimes, because it forces the dc operating point to be the same at the input and output this is similar to find the loop gain for stability analysis.
Look at the location of the ac source now:. Dec 248: May I ask you for what purpose you have a resistor in the feedback path? You have to make a tradeoff. I am ‘injecting’ a voltage and measure the gain around the loop.
Go in there and change it to, say, uV—you’ll see what the effect of datasueet offset voltage is, a real limitation.
LF356 JFET Op Amp IC
Its offset voltage is listed at uV max on the datasheet they use about 40uV in the LTSpice model and it does not saturate your output in simulation:. I think in the model, they use a value of datasheey for the offset voltage.
What I want is the high gain as much as possible at low f and a constant gain at relative high f. This material is intended for free software support.
Its offset voltage is listed at uV max on the datasheet they use about 40uV in the LTSpice model and lf36 does not saturate your output in simulation: