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Questions tagged [sallen-key]

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0answers
59 views

Is this a Sallen-Key High Pass Filter? [closed]

I made the simulation of this filter. I got the values and gain as expected. The only strange AC sweep analysis is that it shows it as a Band Pass Filter while it should be High Pass Filter Is there ...
14
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4answers
2k views

Active low-pass filters — good to what frequencies?

Appendix E of The Art of Electronics, 3rd Edition (LC Butterworth filters) starts by saying that "active filters are convenient at low-frequencies but impractical at higher frequencies". They go and ...
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2answers
71 views

Why is the cutoff frequency of this highpass filter with formula different from LTspice?

I used this online tool to play around and design a Sallen-Key low pass filter with a cutoff frequency of 0.3Hz. When I now put the resulting values for R1, R2, C1 and C2 in the formula I get exactly ...
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2answers
85 views

Does this Sallen and Key filter work on a single supply and does the input offset matter?

This is the schematic for a Sallen and Key from the Doepfer Musikelektronik website: simulate this circuit – Schematic created using CircuitLab I intend to run this in a synth, the oscillators ...
6
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5answers
786 views

Circuit for small level voltage detection (microvolts)

I have been working on a project lately which help in the detection myogenic potentials (of the levels of micro-volts). After studying from several places, I finalized the following test circuit. The ...
1
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2answers
74 views

Sallen-Key - how opamp input bias current changes cutoff frequency?

As in the title: what exactly is the impact of input bias current in Sallen-Key topology, for example the one below: I read that it can matter significantly, however I did not find anything more on ...
0
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1answer
196 views

Input impedance of low pass filter on LTspice must be constant in it's pass band?

I have single supplied sallen-key filter more that have nice 3MHz flat LPF response. I tried to compute the resistance directly by dividing the input voltage by input current which is the voltage and ...
0
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2answers
113 views

What is the difference between a Sallen-Key Band pass filter and a band pass filter?

Am currently doing an assignment on sine wave generation and am using a sallen key band pass filter - i am unsure what the difference between the band pass filter and the sallen-key band pass.
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1answer
177 views

Sallen-Key filter for PT100 RTD measurement

I am going to build temperature sensing system using PT100 sensor (and later Raspberry PI 3). I refer my work to Microchip note AN687 Precision Temperature-Sensing With RTD Circuits. On the page 4 is ...
0
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1answer
64 views

LTC1966 Sallen-Key post-filtering application question

Just a quick question about an application circuit in the LTC1966 datasheet. Figure 13 on page 18 shows a third order (when considering output resistance of the LTC1966) Sallen-Key filter, with a ...
2
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0answers
150 views

Does Sallen-Key filter need a high impedance load?

I am using the circuit below to monitor the output of a piezoelectric diaphragm, represented by a sine wave generator and capacitor C3. The circuit is powered from a split supply (+5V/-5V) derived ...
2
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2answers
177 views

Circuit for Inverse Chebyshev or Elliptic LPF

I know I came across a 2 op-amp, 2 capacitor circuit that can be used for a single section of an Inverse Chebyshev (a.k.a. "Chebyshev Type II) or an Elliptic (Cauer) filter. It has a pair of zeros on ...
2
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5answers
307 views

Does the Sallen-key filter require a buffer for low power applications?

I am designing a circuit which takes an 3uV at 10-10kHz input that filters, applies gain and integrates the analogue signal. I'm thinking of using the circuit below for the topology using two stages ...