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70 Threads found on Sallen Key
It is a unity-gain sallen-key lowpass topology. Thanks! I guess I can cascade two of these to get a steeper roll off?
Hi, What does the underlined sentence mean, please? Inexperience would make me think that the corner frequency of the buffer input, the biasing stage which creates a high-pass, would need to be high(er) with respect to the low-pass corner frequency, to avoid blocking/attenuating the signal of interest, not "...low versus the corner frequency of
Hello, I simulated biased and unbiased sallen-key high-pass filters and got different responce curves. I will be grateful if someone could point out on my error with biasing. Please, find attached unbiased (double source V-=-V+) and biased (single source V-=GND) schematics. Thanks in advance Truffaldino
Thanks for the reply. Is there any similar circuits with a gain not dependent on the frequency? I tried a 2nd order sallen key filter. The problem with the sallen key is that I need an offset of 1.5V at the output of the filter. To obtain this I need to apply -1.5V at the negative input of the op-amp. This is not possible (...)
You didn't even tell about the filter topology (e.g. sallen key, MFB) used by the tools. How could we answer the question? Generally, the same filter characteristic can be implemented with different circuits. Why don't you show both circuits?
hello I am trying to make a demonstration for electrical dept. students and to show them a response of a real second order system, and for some reasons I chose sallen key. I built it on bread board. R1= 10k, R2 = 100k, C1=100uf, C2=1uf. when I give square wave (from arduino) input I get a response that look similar to second order, but with
Why would you design it yourself instead of choosing an off-the-shelf part? For 4 bits, it could be easier to generate a PWM with 4 bit encoded duty cycle and run it though an active low pass filter (i.e. sallen-key works pretty well for this application).
Hi, it is a 2nd order sallen key low pass filter. If your connections are right, then it should have an input range of about +/- 200V. Is your R7 able to dissipate 30W of power? Connect GND_Ref (C1, R3) for the OPAMP directely with extra wire to R8. Connect R2 directely with extra wire to R8. Klaus
For a given amplifier configuration, linearity of a circuit depends on signal amplitudes only. And the amplifier should have sufficient signal feedback. The last requirements requires low opamp gain (e.g. sallen-key configuration or GIC topologies)
The sallen key topology doesn't support gain below unity, adding a voltage divider will of course work, as suggested. A multiple-feedback (MFB) topology gives the option of setting a lower gain, but I fear it's not supported by the Webbench designer.
Hello all, I'm starting an active filter design with in .18u technology. Its a low pass butterworth approximation with 0dB gain and with frequency tuning capability. I'm confused about selecting the topology for the implementation. There are topologies like sallen?key topology,Tow-Thomas biquad filter topology and Multiple feedback topology. Fo
Hello, I am designing a sallen-key filter for one of my projects. I am looking for a very low-noise, low power Operational amplifier for this filter. There are a lot of op-amps out there and I am having hard time choosing one. Any recommended op-amp for such filter? Please find attached document where the schematics of the filter is presented
hmmm yes, now I got it . the transfer function of a cascaded RC second order Low pass filter is by nature 1/((T1S+1)(T2S+2)) so it can be either over damped or critically damped, but it will never oscillates because these 2 poles are always real. Yes - correct. But with the componenets you have used in your circui
Hi, I need help to determine the transfer function for a sallen-key low pass filter. I need help step by step for the mathematics steps for the transfer function. The circuit is this: 110434 The steps i already have and end up with, is this. \begin{equation} V_{out}\cdot \left(\dfrac{\left(G_3+sC_4\right)
Below is a simulation of a simple single-supply precision full-wave rectifier into a Bessel 2nd-order sallen-key 10Hz low-pass filter. It has a ripple of less than 1mVpp with a 1Vpk 200Hz signal. The settling time for a change in the signal level is about 100ms. It uses a single quad LM324 op amp package. The filter was designed using the fre
One filter produces a -3dB cutoff frequency. The filters are completely separate so two of then will add and make their total cutoff frequency -6dB so the -3dB cutoff is at a lower frequency. A sallen-key Butterworth filter with two RC stages uses positive feedback to boost the level of the cutoff frequency of each stage so it is -3dB instead of -6
why are resistor same values for sallen key filter when designing ?
Hello, I was replacing a active Lowpass filter with a sallen-key lowpass filter but the sallenkey-filterLPfilter output was a 2.98V(DC) while the active lowpass filter was having a good pulse output. Activelowpass filter 99687
The signal source of the sallen-key lowpass filter must be much lower than the input impedance of the circuit. Frequently the very low output impedance of an opamp drives it.
Generally speaking, a sallen-key topology is well suited for active filters with CFB OPs. I presume you understand the role of feedback resistor in CFB circuits for loop gain setup. The suggested Rf range should be kept also in filter designs. You also find examples of active filters in CFB OP datasheets, e.g. TI THS3001.