Well for that type of circuit I never use a breadboard ! I am a Ham and know VHF issues. But it is very sensitive so who knows what it may detect? Again depending on your environment. Finally, offset cancellation technique is implemented in an operational amplifier (Op Amp) circuit with further analysis and comparison to prove the methodology. The easiest way is getting the 'AD8307 module' that Zim referenced. The op-amp is so sensitive to the input voltage that at times the output will generate a signal even when there is no intentional input. Depending on your electronic envirenment, FM-stations, TV-transmitters, cell towers etc, you may end up getting some strange readings. Offset null is a calibration feature of the op-amp. In this video, Input offset voltage in op-amp has been explained.This input offset voltage is one of the DC offsets in op-amp.DC offset is the unwanted DC ou. 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. In that case, how to connect it to te preamp ? Typical offset voltages (with both inputs connected together) can be around 1 mV, although some precision operational amplifier chips may have offset voltages of around 10volts. This is known as the input 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. The output can be made completely zero if a small offset voltage is applied to the inputs.

Op amp offset voltage