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67 Threads found on edaboard.com: Input Impedance Measurement
The analog input impedance of the PIC is very high. The reason for the 10K "recommended" limit is because the pin goes through an analog switch matrix to route the pin to a sample and hold circuit. The S&H 'snapshots' the voltage so it can't change while the measurement is being taken. It uses a capacitor to hold the voltage sample and that (...)
there are differential op amps that actually work pretty high in frequency, like 2.3 GHz for the ADA4927-1 from analog devices. Maybe use those. You could convert to single ended signal after the input op amp.
Problem is also that the bridge requires sine rather than square wave input. A filter (e.g. low-pass) is required. Could insert an amplifier too.
Some really basic measurement experiment with my MiniVNA Tiny analyzer. After careful calibration of the VNA, I wanted to check how the input impedance up to 500MHz of a 4m long RG58 cable, terminated on a 50 Ohm dummy load varies. To my surprise I noticed that the SWR response was not flat at all. Actually it was fluctuating so much (...)
What kind of measurement instruments do you have available? You can terminate the transmission line with a resistor in the range of the expected transmission line impedance and measure the input impedance versus frequency. ZL can be determined from the observed minimal and maximal impedance (...)
circa 70's-80's , I used to measure input impedance by using the scope X sweep out on the back to drive an FM input sweep generator then examine the envelope ratio on the scope for a linear frequency response. I got fancier by using X sweep out into Channel 1 then use CH1 Out on back of scope to FM input on Sig Gen so I (...)
Hi, read below "similar threads" In my eyes measuring this voltage makes no sense, because it is "floating". The voltage ins inpredictable an may change any time. (Caused by airflow, humidity, touching, connections of other floating devices...) Additionally the measurement device usually has a finite input impedance, so the (...)
I am using a bridge rectifier(BR1010) for rectification in my project....I am getting some strange results while applying certain voltage as well as when there is no supply voltage..I am not using any input or output filter...Below attached is my schematic 1)Why is the output voltage like this when supply is present??? is it because of absence
Troubleshooting boards that are inoperative To test each stages IC inputs and output incircuit I tried using my Digital meter and set it to ohm to measure the IC op amps input The IC op amps input pins should be in the meg ohms from the the datasheets say for a 741 op amp out of circuit input pin test: To (...)
Dear All I have a slight problem in my design, I am trying to design a 25W PA from 10MHz to 512MHz and did some AWR simulation, Steps are given below 1- IV Curve to bias point 2- Stabilize FET 3- Find input impedance and its conjugate 4- Do Load Pull measurement using AWRDE Load-Pull wizard now after doing all that I got (...)
thanks for reply. Yes, you right in the datasheet already mentioned input impedance. But in my case, the output power at antenna is low ~ 3-4 dBm than expected. I able to control (change) transmission power but I have some concern that ESD protection circuit or shunt cap inside of RF IC is damaged and made some impedance mismatching which (...)
dear all We are trying to set up a calibration procedure for the measurement of transfer impedance of ESD Target. For this we are following the IEC 61000-4-2 edition 2 Standard. This procedure is based on the set up given in this standard. In the set up, a current source is given at the input side which gives the current to the target . (...)
I built up simple inverting-Amplifier with LM358 which Gain is R2/R1 = 26. input voltage is 20mV fixed and hence output voltage should be approximately 520mV. the problem is that the output voltage changes over time while the temperature(25C) and other circumstances are stable. for instance, if output is 520mV today, next week it changes to 530mV
The frequency is not negative, your oscillator doesn't work.That's why the output level is too low and of course it shows negative numbers in dBm (remember dBm is a logarithmic measurement, the levels which are smaller than 1mW are always negative in dBm). Have you ever checked the input impedance of the active part ?? For start-up condition
At 300mW you won't need any further amplification to measure the frequency. What is the input impedance of your frequency counter? It's probably a safe bet - and especially given its low working frequency - to assume it's high (...perhaps of order ~1Mohm?) The most important thing to be done for the measurement is to make sure the (...)
Hello! I have download a pspice model of a commercial opamp. I would like to know how to calculate the input impedence of the opamp using pspice. My model has 5 ports. 2 inputs, 2 voltage supply ports and 1 output. Thanks
Hello friends, I am new in antenna design and I am trying to design a layered MLA for a mobile handset. I prepare my design according to a paper and do some modifications in sizes. I use HFSS 13 for simulation and I started to use HFSS with this project. I used wave port as excitaions and radiation in a sphere. Here is my design and you can se
You did read the ADuCM360 absolute input voltage specification? It's 100 mV in buffered mode, so your measurement probably won't work in this mode. I can generally confirm that the ADuC analog front end works as specified. Without knowing your exact circuit and ADC configuration, it's hard to say what's wrong in your application.
The most plausible explanation is that your multimeter has about 10 MOhm input impedance, and you switched it between input and output. You need to connect an equivalent load instead of the multimeter to get the same input voltage when the multimeter is disconnected... To suggest a measurement trick: If (...)
input impedance is a differential quantity dV/dI rather than the ratio of input voltage and current V/I. The shown multimeter measurement will mainly reflect the OP input current in combination with the meter's test voltage. The real impedance will be around the datasheet value of (...)