# Search results

1. ### Waveguide isolator and coupler manufacturers

Hi, we are looking to purchase WR12 waveguide isolator and couplers. Being new to waveguides, can anyone recommend some reputable companies that manufactures these components?
2. ### [SOLVED] Single ended to differential signal conversion

Hi all, May I know why the following circuit output common mode voltage is not 0.9 V?
3. ### Modified distribution from normal distribution

Hi all, what do you call the distribution generated from these steps: 1. Generate a normal distribution with mean = 0 and standard deviation = 1. 2. Make all the negative data from the distribution positive, i.e. magnitude or absolute the number. 3. Plot the new distribution that now contains...
4. ### Output impedance of opamp

Hi all, what we have learnt is that the output impedance of an opamp is very small. I cannot seem the find this information in the datasheet of the opamp I am looking at. May I know how can I measure the output impedance of an opamp using only spice?
5. ### [SOLVED] Op-amp voltage follower not following input

Hi, I have a simple op-amp voltage follower using OPA683. When the op-amp is powered by +3.3 V and -3.3 V supplies, the ouput voltage maxed out at ~200 mV when I change the input from 0 V to 1 V. But when I change the power supply to +5 V and -5 V, the output follows the input. Any idea why...
6. ### Why we use 50MHz as a reference?

Hi, Why in measuring RF power, a commonly used reference is 50MHz? Why not 100MHz or 60MHz or 55MHz? Thanks.
7. ### Difference between average and CW power

Hi all, When measuring RF power using a power meter and power sensor, what is the difference between average power and CW power? For a sine wave type of signal, is the average power and CW power the same thing? What about for a pulsed signal like GSM, which I suppose there will be no CW power...
8. ### Capacitors operating frequency

Hi all, how do I know what is the maximum frequency that a particular capacitor can handle? Some datasheets I came across don't specify this thing. I need to find capacitors that will be able to work up to 5GHz. Thanks.
9. ### Importance of RF chokes

Hi, what is the use of RF chokes? Is it to block the RF power from interfering with the DC bias network? What will happen if the amplifier has no RF chokes? For wideband amplifiers, is it important to use RF chokes? Thanks.
10. ### Stabilizing output port of a wideband LNA

Just wanted to ask if it's possible to stabilize an amplifier by placing a shunt resistor at the output of the amplifier. I notice that all the RF power will be shunted to ground if I place the resistor there. Adding a series inductor choke to the resistor didn't help at all, the S21 is still...
11. ### How to know whether the FET is a depletion or enhancement type?

Hi, how do I know whether the FET is a depletion or enhancement type? Which type is the PHEMT?
12. ### Strange results of S-parameter simulation

bfp405 unstable amplifier Hi, I am doing a S-parameter simulation for a wideband LNA. But the problem is the simulation results is far from expectation. I am using Siemens BFP405 transistor. I have used some RF chokes for the DC biasing circuit and two DC blocking capacitors. What is the...
13. ### ADS warning message: Resistor Q1.Re2 is shorted.

ADS warning message Hi, I am just wondering what is the meaning of this error message when I simulate a circuit in ADS: Warning detected by HPEESOFSIM during netlist parsing. Resistor Q1.Re2 is shorted. The transistor is Siemens BFP405. I can still view the simulation results though. Thanks.
14. ### Selecting a Wideband LNA Transistor

lna bfr540 Hi, how do I select a suitable transistor for a wideband LNA with a bandwidth from 1GHz to 6GHz? Since the upper frequency is 6GHz, I assume the minimum transition frequency should be 12GHz. Is it necessary to do so? Do I need to select a transistor that is specifically made for...
15. ### What are the 4 pins in RF transistor for?

Hi, I often encounter RF transistors with 4 pins instead of the usual 3 pins. 2 of the pins are emitter pins. Why are the 4 pins? How do I use the 2 emitter pins?
16. ### Books about ultrawideband LNAs

Anyone knows what other books should I read to design an ultrawideband low noise amplifier? I have Microwave Circuit Design by Vendelin, Pavio and Rohde and High Frequency Techniques by Joseph F. White with me.