Products Home / Electrical and Shielding Tools and Supplies / Passive Electrical Filters / Low-Pass Electrical Filters, BNC FeedthroughLow-Pass Electrical Filters, BNC Feedthrough
- Passive Low-Pass Electrical Filters
- Rejection: 40 dB Minimum, 60 dB Typical
- Terminates Directly into High-Impedance Test Equipment
- 1 dB Cutoff Frequencies Available from 1 kHz to 15 MHz
EF120
DC to 10 kHz Low-Pass Filter
Application Idea
EF502 Used in Conjunction with a High-Impedance Oscilloscope and Amplified Photodetector
EF502
DC to 100 kHz Low-Pass Filter
Please Wait
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Figure 1: Each EF100 Series in-line filter features two female BNC connectors. They are engraved with the part number, the type of filter, the passband range, and the response curve.
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Figure 2: Each EF500 Series coaxial filter has a male and female BNC connector. They are engraved with the part number, the type of filter, the passband range, and the response curve.
| Electrical Filters Selection Guide |
|---|
| Low-Pass Electrical Filters |
| High-Pass Electrical Filters |
| DC Block and Mains Hum Electrical Filters |
| DC Block Filter for RF |
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The graph above shows a signal taken on an oscilloscope with (blue trace) and without (red trace) using a filter. The observed phase shift is introduced by the filter.
Features
- 5th Order Elliptic Low-Pass Filter Design
- Selection of 1 dB Passband Windows from 1 kHz to 15 MHz
- Can be Driven by Any 50 Ω Load
- Designed to be Terminated into High-Impedance Equipment
- No External Power Supply Required
Thorlabs' Passive Electrical Filters are feedthrough BNC filters that allow the user to filter unwanted signals and noise with a guaranteed minimum rejection of 40 dB. These low-pass filters are designed to be driven by a low-impedance source and terminated directly into high-impedance equipment. Examples of typical 50 Ω (low-impedance) sources are Thorlabs' amplified photodetectors, while examples of high-impedance equipment include 1 MΩ oscilloscope terminals, DAQ boards, and 100 kΩ op-amp inputs. This page contains our series of low-pass electrical filters. Thorlabs also offers high-pass electrical filters and DC block electrical filters.
These are passive filters; therefore, no power supply is needed to run these devices. Additionally, they will not display any of the intermodulation distortions that are often observed when using active filters. Passive filters also have lower noise floors and lower thermal emission than their active counterparts, giving these filters higher signal-to-noise capabilities. Each filter is engraved with the part number, passband range, input/output impedance values, and a frequency response curve.
High-Order Elliptic Filters
To ensure excellent suppression of frequencies in the stopband region, our 5th order low-pass filters are designed as high-order elliptic filters, providing excellent suppression of high frequency signals. The tables below include more information, such as the 3 dB, 30 dB, and 40 dB stopband frequencies.
Elliptic filters, also known as Cauer filters, produce some of the steepest signal attenuations after the passband when compared to most other passive filters (see the tables below for the filter's frequency response). This property ensures that these filters are well suited for applications that require severe attenuation of stopband frequencies close to the passband.
In-Line and Coaxial Package Designs
Thorlabs offers both in-line and coaxial BNC feedthrough styled filters (see Figures 1 and 2 to the right). The EF100 series filters are in-line and feature a box design with two female BNC connectors. The in-line design is intended to be used in between two BNC cables. The EF500 series filters are coaxial and feature a cylindrical design with a male and female BNC connector. This allows the filter to be directly attached to a device, such as an oscilloscope (see image above). Due to the larger size of the in-line filters, it is not recommended that these filters be attached directly to a measurement device. The larger size of in-line filters over coaxial filters is due to the inverse relationship between the filter frequency and the size of the internal electrical components inside the housing.
| Posted Comments: | |
wangkunpeng
(posted 2018-10-10 18:22:50.577) Hello, we would like to know the max. allowed current of these filters, or specifically for EF502 and EF120. YLohia
(posted 2018-10-10 11:26:53.0) Hello, the filter is rated for 10V max, and the output impedance is rated for 100 kΩ. The max current could be considered as 0.1 mA at DC or anywhere in the transparent or pass-band up to 500 MHz max. Please note that these filters are designed as voltage transfer systems, not to move current. melanie
(posted 2018-09-18 11:02:48.54) Would you consider marketing a low pass filter that also includes DC block ?
I notice you sell separate filters for each, but if I connected them in series I think there would be an impedance mismatch. YLohia
(posted 2018-09-19 02:27:39.0) Hello, thank you for contacting Thorlabs. I will reach out to you directly to discuss your requirements and the possibility of offering this. william.bowden
(posted 2018-07-03 11:39:04.52) It would be helpful if you gave group delay rather that group delay variation. If you are using these in feedback application, it helps to know group delay.
I am interested in the:
EF501
EF526 YLohia
(posted 2018-07-17 03:10:55.0) Response from Yashasvi at Thorlabs USA: Hello, thank you for contacting Thorlabs. Unfortunately, measuring the group delay directly is not quite straightforward, since any test system adds its own group delay and there is considerable uncertainty in knowing what components of the total delay are from the DUT as opposed to the test system itself. The ideal Network Transfer Function can be used to estimate the group/phase delay, but please note that the actual performance of the filters will typically be much better than the ideal transfer functions would indicate. In theory, one can fit a damping function to the ideal curve to match either the sample data on the Spec Sheet or the actual unit.
The group delay can be theoretically calculated from the transfer function when S=iω (where i is the imaginary unit, and ω is the signal angular frequency. The phase delay is ϕ(ω)=arg(f(S)) where arg is the argument operator (returns the angle that the imaginary vector f(S) makes with the +x axis, e.g. arg(c)=arctan(Im(c)/Re(c)) where c is a complex number in the first quadrant). The group delay is then the familiar dϕ(ω)/dω.
I have reached out to you directly with the ideal Network Transfer Functions for EF501 and EF526. mkirchner
(posted 2017-02-14 12:28:05.11) It would be good if you could include the phase response of these electrical filters along with the amplitude response. Some applications care about both the amplitude and phase properties. tfrisch
(posted 2017-02-17 02:01:16.0) Hello, thank you for contacting Thorlabs. I will reach out to you directly regarding the phase response of these filters. coen
(posted 2015-10-29 13:34:59.363) Dear Madame/Sir,
I would be very interested in a low-pass filter with a cutoff of 10 kHz (anti-aliasing of audio signals). Would it be possible to modify the existing EF502?
Kindest regards,
Coen Elemans
Dept of Biology, SDU Denmark besembeson
(posted 2015-11-04 02:18:05.0) Response from Bweh at Thorlabs USA: This will be possible. The housing may look different for such lower frequency cutoffs and we will also need to know an acceptable rejection level for your application. Our Sweden office will be in contact with you. lamarche.louis
(posted 2015-04-10 14:09:55.26) Hello,
Could you send me an approximate analytic transfer
function in the laplace domain for the EF256.
I need to know if there will any ringing on my signal.
Thank you for your help
Regards.
450-652-8077 jlow
(posted 2015-04-27 01:40:40.0) Response from Jeremy at Thorlabs: Yes, we will send you the transfer function via e-mail. |
ZoomThe in-line package of these filters offers two female BNC connectors.
| Item #a | EF110 | EF112 | EF114 | EF120 | EF122 | EF124 |
|---|---|---|---|---|---|---|
| 1 dB Passband Window | DC to 1 kHz | DC to 2 kHz | DC to 5 kHz | DC to 10 kHz | DC to 20 kHz | DC to 50 kHz |
| 3 dB Rejection | >2.05 kHz | >2.76 kHz | >6.61 kHz | >15.2 kHz | >27.2 kHz | >68.4 kHz |
| 30 dB Rejection | >3.1 kHz | >4.27 kHz | >9.95 kHz | >24.5 kHz | >41.6 kHz | >102.1 kHz |
| 40 dB Rejectionb | >4.1 kHz | >6.20 kHz | >11.14 kHz | >27.2 kHz | >45.4 kHz | >109.5 kHz |
| Frequency Response Curve (Click for Graph) |
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| Source Impedance (Typical) | 50 Ω | |||||
| Load Impedance (Typical)c | ≥100 kΩ | |||||
| Input Voltage (Maximum) | ±10 V | |||||
| Storage Temperature | -20 to 70 °C | |||||
ZoomThe coaxial package of these filters offers one male and one female BNC connector.
| Item #a | EF502 | EF504 | EF506 | EF508 | EF510 | EF516 | EF501 | EF526 |
|---|---|---|---|---|---|---|---|---|
| 1 dB Passband Window | DC to 100 kHz | DC to 240 kHz | DC to 500 kHz | DC to 1 MHz | DC to 1.7 MHz | DC to 4.5 MHz | DC to 10 MHz | DC to 15 MHz |
| 3 dB Rejection | >139 kHz | >310 kHz | >640 kHz | >1.35 MHz | >2.3 MHz | >6 MHz | >12 MHz | >21.5 MHz |
| 30 dB Rejection | >199 kHz | >475 kHz | >1 MHz | >2.1 MHz | >3.4 MHz | >9.5 MHz | >20 MHz | >34 MHz |
| 40 dB Rejectionb | >220 kHz | >515 kHz | >1.1 MHz | >2.3 MHz | >3.6 MHz | >10.5 MHz | >22 MHz | >37 MHz |
| Frequency Response Curve (Click for Graph) |
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| Source Impedance (Typical) | 50 Ω | |||||||
| Load Impedance (Typical)c | ≥100 kΩ | |||||||
| Input Voltage (Maximum) | ±10 V | |||||||
| Storage Temperature | -20 to 70 °C | |||||||
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Aluminum Clamps, Post Mountable
These anodized aluminum clamps provide secure mounting for the in-line filters sold above. Each clamp can snap onto the side of the device and the flexure lock can be tightened using the 2 mm (5/64") hex locking screw on the side. The ECM100 fits onto the 1.00" side, while the ECM125 fits onto the 1.25" side.
Each clamp has a #8 (M4) counterbore on the bottom, allowing it to be mounted on a Ø1/2" post or any surface with an 8-32 (M4) tap. The clamp must be mounted via the counterbore before the device is attached, as the counterbore will not be accessible once the housing is secured in the clamp.
Plastic Clamp, Double Sided
The EPS125 clamp is designed to connect two in-line filters for compact setups; the clamp attaches to the 1.25" side of each device.
 Low-Pass Electrical Filters |