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I'm working for a high frequency input signal integrator with AD8041 or LT1364 and doing simulations on LTspice(I'm new for it), AD8041 has properties of 160MHz GBP and LT1364 has 70MHz GBP. They both have some strange results. My circuit is shown as follows. enter image description here

As the integration function shows: $$v_{o} = \frac{1}{RC}\int_{0}^{t}sin\omega tdt$$ I want to make the coefficient equal to 1 So RC = 100k*10u = 1. However, I wonder whether it works well at frequency higher than 1Hz (which is constrained by $$RC >> \Delta t$$), because its Frequency Response is very low at frequency higher than 1. (which is constrained by $$f_{cut} = \frac{1}{RC}$$) Maybe it works but has very small Magnitude. So I input a Sinusoidal Signal with 10Hz. I also add the Parallel Resistors R1 and R4, and the Balanced Resistors R2 and R5.The result is shown as follows.enter image description hereenter image description here In theory, they maybe both begin with 0V and have consistent dc offset. However the plot shows not. I'm curious of the reason and how to remove it. The unwanted dc offset will influence the integration result when the input signal has a dc offset. When the frequency is higher, the offset is very clear in the next picture.(The frequency is 100Hz)enter image description here And it failed when the frequency up to 1Meg！ enter image description here

If my parameter set is unreasonable, please give me some advice. How to design an integrator with high frequency input signal up to 1MHz?

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Here is what you can do ... Made with microcap v12
Note that offset may be influenced by amplitude of input wave.

enter image description here

Forget it for 1 MHz, signals are below -100 dB ...

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  • \$\begingroup\$ Thank you for your guidance! That is to say, if I want it to work at high frequencies, I need to increase its gain?But the amplitude may be very large if it has enough gain(thinking...)1MHz is impossible?(T^T...) \$\endgroup\$ Commented Apr 28, 2024 at 13:40
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    \$\begingroup\$ What are you trying to accomplish? An integrator smooths the variations in a signal, so at high frequency of course it has little output. \$\endgroup\$ Commented Apr 28, 2024 at 14:43
  • \$\begingroup\$ I want to design an integrator that can work with large bandwidth(about 1MHz or more), which is used to complete some Maths' computation no matter what frequency is entered. So the high frequencies is needed, I wonder if it is possible to accomlish? \$\endgroup\$ Commented Apr 28, 2024 at 15:05
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    \$\begingroup\$ The value of your first equation is vo=-cos(wt) /(RCw) ... where the value of w can be 1 MHz*2*Pi. The result should then be -cos(wt)*(1E-6)/(2*Pi) ... Very small. \$\endgroup\$ Commented Apr 28, 2024 at 17:00
  • \$\begingroup\$ So setting the RC = 1 may be unreasonable, I think I know what I shoud do.Thank you! \$\endgroup\$ Commented Apr 28, 2024 at 23:41

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