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I thought that impedance matching is always needed but seems that it is not the case, and in fact seeking matching in some cases will cause troubles.
Can you please give few examples for when matching is not mandatory, or may be the other way around, when matching is a must.
For example, I...
I am trying to use QUCS to simulate the input and output impedance of a simple common emitter amplifier based on BFP420. As this is new to me, I would like to verify with the experts if the steps I performed are the right ones.
I created a schematic with the amplifier I want, and updated all...
Thank you. If we focus more on its use as a low noise front end in a receiver (88-108MHz), would it be a better choice than a BJT taking into consideration that the supply voltage is 5V?
Assuming I am given a specific target gain and noise figure for this front end, can I reach the same target...
Thank you for the response. I was seeing things differently, but will rethink it again.
When I look at figure A, and imagine high frequency noise super imposed on Vcc from somewhere else, this noise would see a least resistance path through the cap rather than through the 100 ohm, and...
I am trying to understand when to use JFET in an RF design. The band in mind is the FM Band (88-108MHz). I have seen statements like "This oscillator will only work using a JFET not a BJT as its active device" and other statements like "for our low noise front end, we will be using a JFET", ...
Reference attached drawing, is the following a correct interpretation of the role of R and C in each figure?
Figure A: The RC is to protect the mic preamp from noise coming from the supply or other parts of the circuit.
Figure B: The RC is to protect the rest of the circuit from any noise...
I followed your proposal, and replaced the C2 with 10nf, and as you advised, the negative resistance disappeared. Of course the input impedance dropped to 400ohm, so no more 1500 ohm input impedance but as I understood from a recent response, I need to replace the transistor with a real RF one...
As a freelance, no student, I have no access or way for even trial versions of ADS or Microwave office to run similar RF simulation. I am mainly using LT Spice but obviously not an RF oriented simulator.
Any recommended free or reasonably priced real RF simulation package?
Practically speaking:
I built the largest possible practical L I could do, and it is 1.8uH (air cored, as I do not have access to the right ferrite core) with a Q of 28, feeding this into SimSmith, I got the C1 and C2 of the Pi network to be 600pf and 154pf (see attached screen shot)
So, I will...
Using the function generator at 10.7Mhz (100mv P2P) and oscilloscope probing at output, I see 300mv (P2P) and in fact the gain increases till 20MHz (400mV PP) then start going down.
I did not see any signs of oscillation on the screen, the current consumption is 3mA of the overall circuit, and I...
I implemented the CE proposed circuit on a PCB, and tried to measure the S11 using a nanoVNA. I got strange results which I am not able to interpret. I am seeing negative resistance, and part of the smith chart is getting out for a good portion of the frequency scan range.
In lot of the FM receivers I see around, come with a simple black wire that you connect to the antenna input of the FM receiver and dangle it. If I use the same wire with an FM receiver I am trying to build, and knowing that the antenna impedance changes depending on a lot of things (length...
The output of the SA612 mixer is 1500 ohm as per datasheet, this output should go into a 10.7MHz ceramic filter which input and output impedance is 330 ohm. This is part of an FM receiver. If I want to have a kind of impedance matching between the two to maintain the power transfer and "I guess...
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