This is the circuit of electromagnetic field sensor which might sense electromagnetic field from 40Hz to 140Hz. The IC LF351 and associated parts forms the pick-up section. 1uH coil L1 is employed for sensing the field and also the IC1 performs required amplification. If the picked electromagnetic field is within audio frequency range, it will be heard through the the top phone Z1. there's also a meter arrangement for correct measuring of the signal strength. Transistor Q1 performs extra amplification on the picked signal in order to drive the meter.
IC LF351 Description
The IC LF351 is a low price high speed JFET input operational amplifier with an internally trimmed input offset voltage (BI-FET II™ technology). The device needs a low supply current and however maintains an oversized gain bandwidth product and a quick slew rate. additionally, compatible high voltage JFET input devices offer terribly low input bias and offset currents. The LF351 is pin compatible with the quality LM741 and uses constant offset voltage adjustment circuitry. This feature permits designers to instantly upgrade the overall performance of existing LM741 styles.
The IC LF351 is also employed in applications like high speed integrators, quick D/A converters, sample-and-hold circuits and lots of different circuits requiring low input offset voltage, low input bias current, high input impedance, high slew rate and wide bandwidth.
Features IC LF351 • Internally trimmed offset voltage: 10 mV
• Low input bias current: 50 pA
• Low input noise voltage: 25 nV/
• Low input noise current: 0.01 pA/
• Wide gain bandwidth: 4 MHz
• High slew rate: 13 V/µs
• Low supply current: 1.8 mA
• High input impedance: 1012 Ohm
• Low total harmonic distortion AV=10,: <0.02% RL=10k, VO=20 Vp-p, BW=20 Hz-20 kHz
• Low 1/f noise corner: 50 Hz
• Fast settling time to 0.01%: 2 µs.
