# filter design

1. ### Should HPF be higher than expected frequency range and LPF lower?

I am confused. In a pulse sensor which I am developing for small animals, where pulse signal can range between 5Hz and 8Hz, I am using an HPF of 5Hz and a LPF of 8Hz. The real signal is somewhere close to 5Hz so I thought maybe 5Hz was way too close a cutoff, and so I proceeded picking Bard's...
2. ### What type of multi-level input filter is used in a 3-phase 30KW vienna PFC?

Hello all, I have been checking this 30 kW Vienna PFC rectifier reference design and didn't understand why all of these filters are used for this kind of application, i mean half of the board is inductors and capacitors for the filters. Can someone explain what type of filters are used? and...
3. ### How to remove HPF from a Photo transistor circuit?

So this below pulse sensor circuit works just fine, but I need to experiment whether the HPF is really necessary as I have tested it with very low HPF values like 0.5Hz and still can see my pulse. Every time I try to remove the HPF by feeding the signal straight to Active LPF stage, my signal...
4. ### Baseline voltage not stabilizing

Hello. I am trying to prepare a filter and amplifier circuit for a strain gauge (Wheatstone bridge in half-bridge configuration). Input power to the Wheatstone bridge is 1 VDC, and each output (+ve and -ve) of the Wheatstone bridge circuit goes the filter. The filter is a second order active...
5. ### Purpose of the Capacitor in this filter

Hi, I do understand that the C5, L3, C6 form a pi filter. But what is the purpose of the other capacitors i.e C8 and C7? What purpose do they serve?
6. ### EMI FILTERS

Hi, We have an power supply card, In that input side we have Adapter, Type C and Lion battery Output side we generate three outputs 5V/2A, 5V/3A X 2. My question is for protecting against internal and external EMI where we need to add filter input side or output side? How to decide that...
7. ### LM386 Input filter trouble

Hello. I am new to electronics and I am trying to complete an LM386 audio amplifier that includes a bandpass filter between 5 and 33 Hz. I know some of the frequencies are outside the frequency range humans can hear. I am testing using a function generator on NI Multisim to get around this. My...

9. ### How we select LC filter for MAX3221?

I have seen a schematic where they used MAX3221, RS232 Driver and Receiver. There they have used LC filter of inductor value 0.68uH and capacitor value of 680pF, but in datasheet they have not mentioned about frequency. Can anyone explain how they selected this value?
10. ### Active filtering circuit design

Hello everyone, I need to design a circuit on breadboard that give filtered outputs as "0.5-4 Hz; 4-7 Hz; 7-12 Hz; 12-30 Hz; 30-100 Hz; 100-1000 Hz" using active filter principles with introducing input signal. Can anyone help me? Thanks in advance.
11. ### Finding correct value of components to get the centre frequency of a band reject filter at 30kHz

Hello! I have to design a band reject filter using two capacitors, two resistors and a load resistor of 1kOhm. I already figured out the appropriate circuit and had derive the transfer function of the filter. I had chose the values for the capacitors, C = 0.01uF and the value of load...
12. ### Non-Inverting Amplifier (AC Coupled) : How to solve this circuit with lower and high frequency?

I need to design this circuit with a gain of 26 for signals where the frequency varies from 800Hz to 8kHz and I also need to find out the current on the RL load. (VA = 100mV) Will C1 behave like an open circuit in ac analysis? I am getting to lower the frequency (800Hz) but I am not able to...
13. ### Digital filter application

Dear all, I designed a digital FIR filter using the frequency sampling method and I got the filter coefficients. Now, I'm working on a real-time (time-domain) application (a numerical simulation) where the time step is varying (depending on the case). In this application the motion of a device...