#How to set op amp offset full#
With R1470k and R2 set to 100 with a 50k, 32 tap, EPOT, the full range of adjustment is 3.2mW and each step is 2mV. The full range of adjustment for Vos is 15V × R2/ (R1+R2). But it is very sensitive so who knows what it may detect? Again depending on your environment. In this circuit, the offset voltage added to the output is Vos (1+Rf/Ri) where Vos is the voltage at the non-inverting input of the op-amp. The easiest way is getting the "AD8307 module" that Zim referenced.
So choose alpha 1 (or bigger, or -1 and add inverter), set beta to required offset and find op amp configuration that maches it. To compensate for an offset voltage by injecting a current you can apply an adjustable voltage from a potentiometer via a high-value resistor to an appropriate. beta (offset) can also be positive/negative. Depending on your electronic envirenment, FM-stations, TV-transmitters, cell towers etc, you may end up getting some strange readings. Op amps allow to change input to output using this formula Vout alpha Vin + beta alpha (multiplier) can be positive/negative, more than 1 or less than 1 in absolute terms. An Off-Set Null circuit is a two terminal balance adjustment on an Op-Amp used to zero or null the output a balanced condition. But - there are many knowledgable people on this board so I'd wait for more people to weigh in on this!Īs for a measuring antenna, a quarter wave whip is approximately 50cm long on 2m. I'd go with the broad band version to see what it can do.
You already have a tuned circuit in there and if you add more, and add gain into the equation, there may be a risk of oscillations. That is a really good question! 144MHz is a high frequency and results may be unpredictable with regard to components and circuit layout if you don't have good measuring equipment. Again, it is important to make sure that the output voltage remains halfway between the two power supply voltages.
#How to set op amp offset how to#
In that case, how to connect it to te preamp ? Where CMRR is equal to the common-mode-rejection-ratio in db: V 1-1 is the first common-mode voltage setting V 1-2 is the second common-mode voltage setting V OS is the measured operational amplifier offset voltage. What is the best : to use the preamp like that as a wide band or to tune it also with a LC circuit.