Dear digikey Service,
I am interested in purchasing the RES SMD 1G OHM, 1%, 0.3W, 1206,] [CRHV1206AF1G00FKE1] resistor from your website.
The datasheet for this resistor does not specify the parasitic capacitance. Could you please provide a typical or maximum value for this parameter?
Thank you for your time and assistance.
Hello @deepthia,
Welcome to the forum.
This is a interesting question. I am very curious to know where you are using such a resistor.
We are unlikely to find an answer to this question as the 1 GΩ resistance is far outside published data. To better understand my statement, please see this paper written by Vishay.
As a general observation, the thick film resistors such as the CRHV series do not appear suited for high frequency work. The accordion like structures that allow high voltage as shown in this document would be prone to inductive and capacitive parasitic with potential for self-resonance at microwave frequencies. Perhaps this is why the datasheet does not mention the reactive properties.
If you are interested in high frequency application, you may find a solution in the Vishay FC series. These thin film resistors are rated for frequency up to 40 GHz.
Best wishes,
APDahlen
P.S. For our readers, here is a good document to add to your library.
Thanks for the insightful response! I appreciate you taking the time to explain the limitations of thick film resistors for high-frequency applications
I am using this resistor in making an amplifier design of 1MHz bandwidth . The thin film resistors are rated for the application of 40GHz ,but in this Gohm range thin film resistors are not available . Thin film resistors range is only upto 1k ohm. This self resonance in high frequency range is it in 1Mhz or greater than 1Mhz ,can you please specify that value clearly?
Do you have any other recommendations for high-frequency resistors suitable for a 1 MHz amplifier application? Perhaps there might be specific models within the FC series that would be a good fit? Any recommendations for 1Gohm resistor operating ideally untill 1Mhz frequency?
Hello,
Here is the list of 1Gohm resistors we have listed in our system and you can see options are limited. As APDahlen mentioned the 1 GΩ resistance is far outside published data for the information you’re seeking on these.
Sorry @deepthia,
I’m at the end of knowledge.
There aren’t many options. The situation stays the same when we shift to through-hole and allow for combinations or resistors.
Thick film appears to be the only viable option and the datasheets exclude high frequency applications.
On the other hand, I understand you are constructing a broadband amplifier with a high frequency cutoff of 1 MHz. In relative terms, 1 MHz isn’t that high. While I can make no promises, I suspect the thick film resistor will be viable for this application.
Sincerely,
Aaron
P.S. Out of curiosity, what is the function of the 1 GΩ in a broadband amplifier. Most designs use low value components. In fact, the bleeder resistor on the main capacitor bank tends to be the highest value.
You’re right, most broadband amplifiers use lower value components. In this specific design, the 1 GΩ resistor is used because ,I want high gain (10^9ohm) transimpedance amplifier , with less noise . So i want to use 1gig ohm resistor .
Hi @deepthia,
Understood. But won’t the thermal noise swamp your design? Also, why not use a constant current source?
BTW, I just purchased a book by Douglas Self. It’s very informative as he covers a considerable amount of theory along with practical information such as lowering the noise floor. You may find it useful as the audio techniques are likely to extend to the low radio frequency spectrum.
Good luck on your project. Please let us know if we can assist.
Sincerely,
Aaron
I want input referred current noise , if resistance is more current referred noise will be less and gain is more . If any how i can know the capacitance of the resistor then i can know how the bandwidth impacts the amplifier . Input referred current noise is okay when i am using 1gig ohm resistor .In my case input is current source .
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